Year 6 Maths reasoning (SATs): Line graphs and readings
Part of the Year 6 Maths reasoning (SATs) statistics and data chapter. Chapter overview · whole chapter on one page
Line graphs and readings
Rule
A line graph joins readings taken over time. To find the change between two times, subtract the earlier reading from the later one.
The steepest part of the line shows the biggest change between two readings.
Key ideas
- Read the value at each time from the graph or table.
- Change = later reading - earlier reading.
- A steep line means a big change over a short time.
| Time | Temperature (degrees C) |
|---|---|
| 6 am | 5 |
| 8 am | 9 |
| 10 am | 14 |
| 12 pm | 17 |
| 2 pm | 15 |
Method. Subtract the earlier reading from the later one.
- Read the two values. At 6 am it is 5 degrees C, and at 12 pm it is 17 degrees C.5 and 17
- Find the change. Subtract the first reading from the second.17 - 5 = 12
- Write the answer. 12 degrees C
Check. 5 + 12 = 17. ✓
Method. Subtract the earlier reading from the later one.
- Read the two values. At Jan it is 20 cm, and at May it is 31 cm.20 and 31
- Find the change. Subtract the first reading from the second.31 - 20 = 11
- Write the answer. 11 cm
Check. 20 + 11 = 31. ✓
Method. Look for the largest value.
- Find the largest value. The largest is 17 degrees.17
- Find its time. 17 degrees is at 12 pm.12 pm
- Write the answer. 12 pm
Check. 17 is the highest reading. ✓
Watch out
Watch out. A line graph shows readings only at the times that were measured. Do not assume what happened between them.
Exam tip
Practice guide. Read each value with a ruler, and check the scale on the axis before you read it.
Exercise 8C Practice: line graphs
Non-calculator| Time | Temperature |
|---|---|
| 6 am | 5 |
| 8 am | 9 |
| 10 am | 14 |
| 12 pm | 17 |
| 2 pm | 15 |
Method. Subtract the earlier reading from the later one.
- Read the two values. At 8 am it is 9 degrees C, and at 2 pm it is 15 degrees C.9 and 15
- Find the change. Subtract the first reading from the second.15 - 9 = 6
- Write the answer. 6 degrees C
Check. 9 + 6 = 15. ✓
| Month | Height (cm) |
|---|---|
| Jan | 20 |
| Mar | 26 |
| May | 31 |
| Jul | 29 |
Method. Subtract the earlier reading from the later one.
- Read the two values. At Mar it is 26 cm, and at Jul it is 29 cm.26 and 29
- Find the change. Subtract the first reading from the second.29 - 26 = 3
- Write the answer. 3 cm
Check. 26 + 3 = 29. ✓
| Time | Temperature |
|---|---|
| 6 am | 5 |
| 8 am | 9 |
| 10 am | 14 |
| 12 pm | 17 |
| 2 pm | 15 |
Method. Read the value at 10 am from the table.
- Find 10 am. The reading at 10 am is 14 degrees.14
- Write the answer. 14
Check. 14 degrees at 10 am. ✓
| Month | Height (cm) |
|---|---|
| Jan | 20 |
| Mar | 26 |
| May | 31 |
| Jul | 29 |
Method. Find the largest change between neighbouring readings.
- Changes. Jan to Mar: 6 cm. Mar to May: 5 cm. May to Jul: 29 - 31 = -2 cm.6, 5, -2
- Largest. The largest change is Jan to Mar, which is 6 cm.Jan to Mar
- Write the answer. Jan to Mar
Check. 26 - 20 = 6. ✓
| Month | Height (cm) |
|---|---|
| Jan | 20 |
| Mar | 26 |
| May | 31 |
| Jul | 29 |
Method. Look for a change of 6.
- Check the changes. Jan to Mar is 26 - 20 = 6 cm.6 cm
- Name the months. The change of 6 cm is from Jan to Mar.Jan to Mar
- Write the answer. Jan to Mar
Check. 26 - 20 = 6. ✓
Method. Think about what the graph shows and what it does not.
- What the graph shows. It shows the readings up to now only.readings so far
- Conclude. A prediction is not certain, so we cannot say for sure.not certain
- Write the answer. No, because the graph only shows the readings so far, and the growth may not stay the same.
Check. Predictions from a graph are not certain. ✓
| Time | Temperature |
|---|---|
| 6 am | 5 |
| 8 am | 9 |
| 10 am | 14 |
| 12 pm | 17 |
| 2 pm | 15 |
Method. Subtract the earlier reading from the later one.
- Subtract. 17 - 9 = 8.8
- Write the answer. 8
Check. 9 + 8 = 17. ✓
Method. Test each choice against the question.
- Read what the question asks. Decide what the answer must do or show.
- Test the choice. 17 degrees at 12 pm is the largest reading in the table.The temperature was highest at 12 pm fits
- Reject the other choices. At 2 pm the reading was 15 degrees, and it fell after 12 pm, so it did not rise every time.The temperature was 20 degrees at 2 pm and The temperature rose every time between readings do not fit
- Write the answer. The temperature was highest at 12 pm
Check. The temperature was highest at 12 pm is the one that fits. ✓
Method. Compare the two readings.
- Compare. July 29 cm is less than May 31 cm.29 < 31
- Decide. The height went down, so the plant did not grow.no
- Write the answer. no
Check. 29 - 31 = -2. ✓
| Time | Temperature |
|---|---|
| 6 am | 5 |
| 8 am | 9 |
| 10 am | 14 |
| 12 pm | 17 |
| 2 pm | 15 |
Method. Subtract the earlier reading from the later one.
- Read the two values. At 10 am it is 14 degrees C, and at 2 pm it is 15 degrees C.14 and 15
- Find the change. Subtract the first reading from the second.15 - 14 = 1
- Write the answer. 1 degrees C
Check. 14 + 1 = 15. ✓