Year 4: Time graphs and continuous data
Part of the Year 4 pictograms, bar charts and time graphs chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
Time graphs and continuous data
There are two kinds of data. Discrete data is data you count. The number of goals in a match is 0, 1, 2, 3 … You cannot score 2½ goals. We often show discrete data in a pictogram or a bar chart.
Continuous data is data you measure. A plant’s height, a temperature or the time for a race can be any value, with lots of values in between. Continuous data changes smoothly, so we can show it on a time graph (also called a line graph).
To read a time graph, find the time along the bottom. Go up to the dot, then across to the scale. At 11am the temperature is 18°C. To find when something happens, do it the other way round: find the number on the scale, go across to the line, then down to the time. At the same time as 12pm and 1pm the line is flat, so the temperature stayed the same.
The line shows the trend: what the numbers are doing over time. If the line goes up, the number is rising. If it goes down, the number is falling. If it is flat, the number stays the same. To draw a time graph, plot a dot for each reading, then join the dots in order with a ruler.
Key ideas
- Discrete data is counted (whole numbers). Continuous data is measured (any value in between).
- A time graph has time along the bottom and the measurement up the side.
- To read a value: go up from the time to the line, then across to the scale. To find a time: go across from the value to the line, then down.
- The line going up means rising. Going down means falling. Flat means no change.
- To find a change, subtract: the bigger reading minus the smaller reading.
Key words. Discrete data is data you count. It jumps from one whole number to the next (you cannot have 2½ pupils). Continuous data is data you measure. It can take any value in between, like a height or a time. Continuous data changes smoothly.
Method. Think about how we get the numbers. We count discrete data. We measure continuous data.
- Ask: do we count it, or measure it? Counting gives whole numbers that jump. Measuring gives numbers that can be anywhere between.We count the children: 24, 25, 26 … whole numbers only.
- Decide. If we count it, it is discrete. If we measure it, it is continuous.It is discrete data.
- Choose a graph. Different data suits different graphs.Discrete data is often shown on a bar chart or pictogram.
Check. Can there be a value in between? No: you cannot have a part of a whole thing. ✓
Watch out. Money is counted in pence, so it is discrete. Time, height and temperature are measured, so they are continuous.
Key words. Discrete data is data you count. It jumps from one whole number to the next (you cannot have 2½ pupils). Continuous data is data you measure. It can take any value in between, like a height or a time. Continuous data changes smoothly.
Method. Think about how we get the numbers. We count discrete data. We measure continuous data.
- Ask: do we count it, or measure it? Counting gives whole numbers that jump. Measuring gives numbers that can be anywhere between.We measure the height with a ruler. It could be 12 cm, 12.5 cm, 12.7 cm … any value in between.
- Decide. If we count it, it is discrete. If we measure it, it is continuous.It is continuous data.
- Choose a graph. Different data suits different graphs.Continuous data is often shown on a time graph (line graph).
Check. Can there be a value in between? Yes: for example, halfway between two values. ✓
Watch out. Money is counted in pence, so it is discrete. Time, height and temperature are measured, so they are continuous.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for 11am.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 11am along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At 11am, the point is exactly on the line for 18°C.
- Write the answer. 11am = 18°C
Check. Look again at the picture: 11am is 18. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Start at 14 on the scale, go across to the line, then go down to find the time.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 14 on the scale up the side. Then go across to the line.Look across from 14 until you reach the line.
- Go down to the time. Look straight down from the point to the numbers along the bottom.The point is above 10am.
- Write the answer. 10am
Check. At 10am the temperature is 14. ✓
Watch out. Go across first, then down.
Key words. The difference between two numbers is how much bigger one is than the other. We find it by subtracting. “How many more” and “how many fewer” questions are difference questions. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. To find “how many more”, read both numbers and then subtract the smaller from the bigger.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read the numbers we need from the picture. We need these numbers for the calculation.12pm = 20
8am = 10 - Find the difference. To find how many more (or fewer), subtract the smaller number from the bigger number.20 − 10 = 10
- Write the answer. 10 °C warmer
Check. Add back: 10 + 10 = 20. ✓
Watch out. Subtract: do not add. The question asks for the difference.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at each part of the line. Say if it goes up, goes down or stays the same.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read every point. We need each number.8am = 10, 9am = 12, 10am = 14, 11am = 18, 12pm = 20, 1pm = 20, 2pm = 16
- Compare each point with the next one. Up if the next number is bigger. Down if it is smaller. The same if the numbers match.8am to 9am: 10 to 12, it goes up
9am to 10am: 12 to 14, it goes up
10am to 11am: 14 to 18, it goes up
11am to 12pm: 18 to 20, it goes up
12pm to 1pm: 20 to 20, it stays the same
1pm to 2pm: 20 to 16, it goes down - Join the parts that are the same. Write short sentences that cover the whole graph.From 8am to 12pm it goes up.
From 12pm to 1pm it stays the same.
From 1pm to 2pm it goes down.
Check. The sentences cover the whole graph from 8am to 2pm. ✓
Watch out. A flat line means the number stays the same.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for Week 3.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 10s.
Between two numbers there are 5 gaps.
10 ÷ 5 = 2, so each small gap is worth 2. - Find Week 3 along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At Week 3, the point is between 10 and 20.
10 + 3 × 2 = 16 cm - Write the answer. Week 3 = 16 cm
Check. Look again at the picture: Week 3 is 16. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
| Week | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| Height (cm) | 2 | 6 | 10 | 16 | 22 | 28 |
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Plot each point: find the time on the bottom, go up to the number, and put a dot. Then join the dots with a ruler.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 10s.
Between two numbers there are 5 gaps.
10 ÷ 5 = 2, so each small gap is worth 2. - Find each point. Find the time along the bottom. Go up to the number. Put a dot there.Week 2: go up to 10 (on the line for 10)
Week 4: go up to 22 (1 gap above 20) - Join the dots. Use a ruler to join each dot to the next one with a straight line.
Check. Read each dot back from your graph. They should match the table. ✓
Watch out. Mark the dots exactly where the lines cross. Then join them in order.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. The line joining two points shows how the number changes. Halfway in time is about halfway in value.
- Read the two points. The time we want is halfway between them.10am = 14, 11am = 18
- Find the number halfway. Halfway between two numbers: add them, then halve. Or add half the difference.14 + 18 = 32, and 32 ÷ 2 = 16
- Write the answer. This is an estimate. We are using the straight line between the points.About 16
Check. 14 and 18 are each 2 away from 16. ✓
Watch out. This gives an estimate. We cannot be sure what happened between the readings.
Watch out
Do not mix up time and measurement. The time is along the bottom. The measurement is up the side. And remember: the line between two dots only shows the trend. We cannot be sure of the exact value there.Exercise 11F Time graphs and continuous data
Non-calculatorKey words. Discrete data is data you count. It jumps from one whole number to the next (you cannot have 2½ pupils). Continuous data is data you measure. It can take any value in between, like a height or a time. Continuous data changes smoothly.
Method. Think about how we get the numbers. We count discrete data. We measure continuous data.
- Ask: do we count it, or measure it? Counting gives whole numbers that jump. Measuring gives numbers that can be anywhere between.We count the goals. It is a whole number.
- Decide. If we count it, it is discrete. If we measure it, it is continuous.It is discrete data.
- Choose a graph. Different data suits different graphs.Discrete data is often shown on a bar chart or pictogram.
Check. Can there be a value in between? No: you cannot have a part of a whole thing. ✓
Watch out. Money is counted in pence, so it is discrete. Time, height and temperature are measured, so they are continuous.
Key words. Discrete data is data you count. It jumps from one whole number to the next (you cannot have 2½ pupils). Continuous data is data you measure. It can take any value in between, like a height or a time. Continuous data changes smoothly.
Method. Think about how we get the numbers. We count discrete data. We measure continuous data.
- Ask: do we count it, or measure it? Counting gives whole numbers that jump. Measuring gives numbers that can be anywhere between.We measure time with a stopwatch. It can be any value in between.
- Decide. If we count it, it is discrete. If we measure it, it is continuous.It is continuous data.
- Choose a graph. Different data suits different graphs.Continuous data is often shown on a time graph (line graph).
Check. Can there be a value in between? Yes: for example, halfway between two values. ✓
Watch out. Money is counted in pence, so it is discrete. Time, height and temperature are measured, so they are continuous.
Key words. Discrete data is data you count. It jumps from one whole number to the next (you cannot have 2½ pupils). Continuous data is data you measure. It can take any value in between, like a height or a time. Continuous data changes smoothly.
Method. Think about how we get the numbers. We count discrete data. We measure continuous data.
- Ask: do we count it, or measure it? Counting gives whole numbers that jump. Measuring gives numbers that can be anywhere between.We count the cars. It is a whole number.
- Decide. If we count it, it is discrete. If we measure it, it is continuous.It is discrete data.
- Choose a graph. Different data suits different graphs.Discrete data is often shown on a bar chart or pictogram.
Check. Can there be a value in between? No: you cannot have a part of a whole thing. ✓
Watch out. Money is counted in pence, so it is discrete. Time, height and temperature are measured, so they are continuous.
Key words. Discrete data is data you count. It jumps from one whole number to the next (you cannot have 2½ pupils). Continuous data is data you measure. It can take any value in between, like a height or a time. Continuous data changes smoothly.
Method. Think about how we get the numbers. We count discrete data. We measure continuous data.
- Ask: do we count it, or measure it? Counting gives whole numbers that jump. Measuring gives numbers that can be anywhere between.We measure temperature with a thermometer. It can be any value in between.
- Decide. If we count it, it is discrete. If we measure it, it is continuous.It is continuous data.
- Choose a graph. Different data suits different graphs.Continuous data is often shown on a time graph (line graph).
Check. Can there be a value in between? Yes: for example, halfway between two values. ✓
Watch out. Money is counted in pence, so it is discrete. Time, height and temperature are measured, so they are continuous.
Key words. Discrete data is data you count. It jumps from one whole number to the next (you cannot have 2½ pupils). Continuous data is data you measure. It can take any value in between, like a height or a time. Continuous data changes smoothly.
Method. Think about how we get the numbers. We count discrete data. We measure continuous data.
- Ask: do we count it, or measure it? Counting gives whole numbers that jump. Measuring gives numbers that can be anywhere between.We measure height with a tape measure. It can be any value in between.
- Decide. If we count it, it is discrete. If we measure it, it is continuous.It is continuous data.
- Choose a graph. Different data suits different graphs.Continuous data is often shown on a time graph (line graph).
Check. Can there be a value in between? Yes: for example, halfway between two values. ✓
Watch out. Money is counted in pence, so it is discrete. Time, height and temperature are measured, so they are continuous.
Key words. Discrete data is data you count. It jumps from one whole number to the next (you cannot have 2½ pupils). Continuous data is data you measure. It can take any value in between, like a height or a time. Continuous data changes smoothly.
Method. Think about how we get the numbers. We count discrete data. We measure continuous data.
- Ask: do we count it, or measure it? Counting gives whole numbers that jump. Measuring gives numbers that can be anywhere between.We count the pages. It is a whole number.
- Decide. If we count it, it is discrete. If we measure it, it is continuous.It is discrete data.
- Choose a graph. Different data suits different graphs.Discrete data is often shown on a bar chart or pictogram.
Check. Can there be a value in between? No: you cannot have a part of a whole thing. ✓
Watch out. Money is counted in pence, so it is discrete. Time, height and temperature are measured, so they are continuous.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for 8am.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 8am along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At 8am, the point is exactly on the line for 10°C.
- Write the answer. 8am = 10°C
Check. Look again at the picture: 8am is 10. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for 9am.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 9am along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At 9am, the point is exactly on the line for 12°C.
- Write the answer. 9am = 12°C
Check. Look again at the picture: 9am is 12. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for 11am.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 11am along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At 11am, the point is exactly on the line for 18°C.
- Write the answer. 11am = 18°C
Check. Look again at the picture: 11am is 18. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for 2pm.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 2pm along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At 2pm, the point is exactly on the line for 16°C.
- Write the answer. 2pm = 16°C
Check. Look again at the picture: 2pm is 16. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Start at 12 on the scale, go across to the line, then go down to find the time.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 12 on the scale up the side. Then go across to the line.Look across from 12 until you reach the line.
- Go down to the time. Look straight down from the point to the numbers along the bottom.The point is above 9am.
- Write the answer. 9am
Check. At 9am the temperature is 12. ✓
Watch out. Go across first, then down.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Start at 18 on the scale, go across to the line, then go down to find the time.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 18 on the scale up the side. Then go across to the line.Look across from 18 until you reach the line.
- Go down to the time. Look straight down from the point to the numbers along the bottom.The point is above 11am.
- Write the answer. 11am
Check. At 11am the temperature is 18. ✓
Watch out. Go across first, then down.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Start at 16 on the scale, go across to the line, then go down to find the time.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 16 on the scale up the side. Then go across to the line.Look across from 16 until you reach the line.
- Go down to the time. Look straight down from the point to the numbers along the bottom.The point is above 2pm.
- Write the answer. 2pm
Check. At 2pm the temperature is 16. ✓
Watch out. Go across first, then down.
Key words. The difference between two numbers is how much bigger one is than the other. We find it by subtracting. “How many more” and “how many fewer” questions are difference questions. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. To find “how many more”, read both numbers and then subtract the smaller from the bigger.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read the numbers we need from the picture. We need these numbers for the calculation.11am = 18
9am = 12 - Find the difference. To find how many more (or fewer), subtract the smaller number from the bigger number.18 − 12 = 6
- Write the answer. 6 °C warmer
Check. Add back: 12 + 6 = 18. ✓
Watch out. Subtract: do not add. The question asks for the difference.
Key words. The difference between two numbers is how much bigger one is than the other. We find it by subtracting. “How many more” and “how many fewer” questions are difference questions. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. To find “how many more”, read both numbers and then subtract the smaller from the bigger.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read the numbers we need from the picture. We need these numbers for the calculation.1pm = 20
2pm = 16 - Find the difference. To find how many more (or fewer), subtract the smaller number from the bigger number.20 − 16 = 4
- Write the answer. 4 °C cooler
Check. Add back: 16 + 4 = 20. ✓
Watch out. Subtract: do not add. The question asks for the difference.
Key words. The difference between two numbers is how much bigger one is than the other. We find it by subtracting. “How many more” and “how many fewer” questions are difference questions. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Find the biggest and the smallest numbers, then subtract.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find the biggest and the smallest. We need these numbers for the calculation.12pm = 20
8am = 10 - Subtract. The difference between two numbers is the bigger minus the smaller.20 − 10 = 10
- Write the answer. 10
Check. 10 + 10 = 20. ✓
Watch out. Be sure you have found the biggest and the smallest of all the numbers.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Read the value at each time, compare, and subtract to find the change.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read both points. We need these numbers for the calculation.8am = 10
10am = 14 - Compare. If the second number is bigger, the line goes up. If it is smaller, the line goes down.10 to 14: it goes up
- Find how much. Subtract the smaller number from the bigger number.14 − 10 = 4
Check. Check the line on the graph between the two times: it goes up. ✓
Watch out. Say whether it goes up or down, and by how much.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Read the value at each time, compare, and subtract to find the change.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read both points. We need these numbers for the calculation.12pm = 20
1pm = 20 - Compare. The two numbers are the same.20 = 20, so it stays the same.
Check. Check the line on the graph between the two times: it is flat. ✓
Watch out. Say whether it goes up or down, and by how much.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Read the value at each time, compare, and subtract to find the change.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read both points. We need these numbers for the calculation.1pm = 20
2pm = 16 - Compare. If the second number is bigger, the line goes up. If it is smaller, the line goes down.20 to 16: it goes down
- Find how much. Subtract the smaller number from the bigger number.20 − 16 = 4
Check. Check the line on the graph between the two times: it goes down. ✓
Watch out. Say whether it goes up or down, and by how much.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Start at 20 on the scale, go across to the line, then go down to find the time.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 20 on the scale up the side. Then go across to the line.Look across from 20 until you reach the line.
- Go down to the time. Look straight down from the point to the numbers along the bottom.The point is above 12pm.
- Write the answer. 12pm
Check. At 12pm the temperature is 20. ✓
Watch out. Go across first, then down.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Read every number, then find the smallest one.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read every number. We need these numbers for the calculation.8am = 10
9am = 12
10am = 14
11am = 18
12pm = 20
1pm = 20
2pm = 16 - Compare the numbers. Look for the smallest number.The smallest number is 10.
- Write the answer. The question asks for the name, not the number.8am
Check. No other number is smaller than 10. ✓
Watch out. The question asks which one, so write the name.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Find the change between each pair of points next to each other. Then pick the biggest.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read every point. We need each number.8am = 10, 9am = 12, 10am = 14, 11am = 18, 12pm = 20, 1pm = 20, 2pm = 16
- Find the change each time. Subtract each number from the next one.8am to 9am: 12 − 10 = 2
9am to 10am: 14 − 12 = 2
10am to 11am: 18 − 14 = 4
11am to 12pm: 20 − 18 = 2
12pm to 1pm: 20 − 20 = 0
1pm to 2pm: 16 − 20 = -4 - Find the biggest change. Choose the largest rise.The biggest rise is 4, between 10am and 11am.
Check. The line is steepest between 10am and 11am. ✓
Watch out. The steepest part of the line is the biggest change.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for Week 1.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 10s.
Between two numbers there are 5 gaps.
10 ÷ 5 = 2, so each small gap is worth 2. - Find Week 1 along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At Week 1, the point is between 0 and 10.
0 + 3 × 2 = 6 cm - Write the answer. Week 1 = 6 cm
Check. Look again at the picture: Week 1 is 6. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for Week 3.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 10s.
Between two numbers there are 5 gaps.
10 ÷ 5 = 2, so each small gap is worth 2. - Find Week 3 along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At Week 3, the point is between 10 and 20.
10 + 3 × 2 = 16 cm - Write the answer. Week 3 = 16 cm
Check. Look again at the picture: Week 3 is 16. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for Week 5.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 10s.
Between two numbers there are 5 gaps.
10 ÷ 5 = 2, so each small gap is worth 2. - Find Week 5 along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At Week 5, the point is between 20 and 30.
20 + 4 × 2 = 28 cm - Write the answer. Week 5 = 28 cm
Check. Look again at the picture: Week 5 is 28. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. The difference between two numbers is how much bigger one is than the other. We find it by subtracting. “How many more” and “how many fewer” questions are difference questions. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. To find “how many more”, read both numbers and then subtract the smaller from the bigger.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 10s.
Between two numbers there are 5 gaps.
10 ÷ 5 = 2, so each small gap is worth 2. - Read the numbers we need from the picture. We need these numbers for the calculation.Week 5 = 28
Week 2 = 10 - Find the difference. To find how many more (or fewer), subtract the smaller number from the bigger number.28 − 10 = 18
- Write the answer. 18 cm
Check. Add back: 10 + 18 = 28. ✓
Watch out. Subtract: do not add. The question asks for the difference.
| Hour | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| Height (cm) | 22 | 18 | 14 | 10 | 6 | 2 |
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Plot each point: find the time on the bottom, go up to the number, and put a dot. Then join the dots with a ruler.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 4s.
Between two numbers there are 2 gaps.
4 ÷ 2 = 2, so each small gap is worth 2. - Find each point. Find the time along the bottom. Go up to the number. Put a dot there.Hour 0: go up to 22 (1 gap above 20)
Hour 1: go up to 18 (1 gap above 16)
Hour 2: go up to 14 (1 gap above 12)
Hour 3: go up to 10 (1 gap above 8)
Hour 4: go up to 6 (1 gap above 4)
Hour 5: go up to 2 (1 gap above 0) - Join the dots. Use a ruler to join each dot to the next one with a straight line.
Check. Read each dot back from your graph. They should match the table. ✓
Watch out. Mark the dots exactly where the lines cross. Then join them in order.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Plot each point: find the time on the bottom, go up to the number, and put a dot. Then join the dots with a ruler.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 4s.
Between two numbers there are 2 gaps.
4 ÷ 2 = 2, so each small gap is worth 2. - Find each point. Find the time along the bottom. Go up to the number. Put a dot there.11am: go up to 12 (on the line for 12)
1pm: go up to 20 (on the line for 20) - Join the dots. Use a ruler to join each dot to the next one with a straight line.
Check. Read each dot back from your graph. They should match the table. ✓
Watch out. Mark the dots exactly where the lines cross. Then join them in order.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for 10:00.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 10:00 along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At 10:00, the point is exactly on the line for 4 km.
- Write the answer. 10:00 = 4 km
Check. Look again at the picture: 10:00 is 4. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at the graph carefully and read off the number for 12:00.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Find 12:00 along the bottom and read the point. Go up from the time to the point on the line, then look across to the scale (follow the orange dotted lines).At 12:00, the point is exactly on the line for 8 km.
- Write the answer. 12:00 = 8 km
Check. Look again at the picture: 12:00 is 8. ✓
Watch out. Read the scale up the side carefully. Check which time you are looking at along the bottom.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. A flat line means nothing changes. Find the flat part, then work out how long it lasts.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Look for a flat part of the line. A flat line means the number does not change.The line is flat from 10:00 to 11:00.
- Check the numbers. They should be the same.10:00 = 4 and 11:00 = 4
Check. The two numbers are both 4. ✓
Watch out. Look for the part of the line that does not go up or down.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Work out the time between the start and the end of the flat line.
- Find the times. The flat line runs from 10:00 to 11:00.10:00 to 11:00
- Work out the time. From 10:00 to 11:00 is one hour.1 hour = 60 minutes
Check. 10:00 + 60 minutes = 11:00. ✓
Watch out. Use the times on the bottom of the graph.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Read the numbers from the graph, then check the statement.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read the points in the statement. Find the numbers on the graph.12pm = 20, 1pm = 20. They are the same.
- Decide. The statement is true.
Check. We read the numbers on the graph. ✓
Watch out. Read the scale carefully.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Read the numbers from the graph, then check the statement.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read the points in the statement. Find the numbers on the graph.11am = 18, 12pm = 20. 20 is more than 18, so it went up, not down.
- Decide. The statement is false.
Check. We read the numbers on the graph. ✓
Watch out. Read the scale carefully.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Read the numbers from the graph, then check the statement.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read the points in the statement. Find the numbers on the graph.8am = 10, 9am = 12. 12 − 10 = 2.
- Decide. The statement is true.
Check. We read the numbers on the graph. ✓
Watch out. Read the scale carefully.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. Look at each part of the line. Say if it goes up, goes down or stays the same.
- Find the scale. The scale up the side tells us what each gridline is worth.The numbers up the side go up in 2s: 0, 2, 4, 6...
- Read every point. We need each number.8am = 10, 9am = 12, 10am = 14, 11am = 18, 12pm = 20, 1pm = 20, 2pm = 16
- Compare each point with the next one. Up if the next number is bigger. Down if it is smaller. The same if the numbers match.8am to 9am: 10 to 12, it goes up
9am to 10am: 12 to 14, it goes up
10am to 11am: 14 to 18, it goes up
11am to 12pm: 18 to 20, it goes up
12pm to 1pm: 20 to 20, it stays the same
1pm to 2pm: 20 to 16, it goes down - Join the parts that are the same. Write short sentences that cover the whole graph.From 8am to 12pm it goes up.
From 12pm to 1pm it stays the same.
From 1pm to 2pm it goes down.
Check. The sentences cover the whole graph from 8am to 2pm. ✓
Watch out. A flat line means the number stays the same.
Key words. A time graph (or line graph) shows how something changes over time. The points are joined by lines. The numbers along the bottom show the time. The numbers up the side show the measurement.
Method. The line between two dots shows the trend. We can estimate halfway, but we cannot be sure.
- Read the points. The readings at 10am and 11am are 14°C and 18°C.10am = 14, 11am = 18
- Find halfway. Add and halve.14 + 18 = 32, and 32 ÷ 2 = 16
- Say what is wrong. No one measured at 10:30. The temperature could have changed in a different way.It is only an estimate: about 16°C.
Check. 16 is halfway between 14 and 18. ✓
Watch out. Between the dots the graph only shows the trend. It is an estimate.