Year 1: Using a ruler and recording lengths
Part of the Year 1 length and height chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
Using a ruler and recording lengths
A ruler measures length in centimetres. We write centimetres as cm. Each big number on the ruler is one centimetre. The small marks between the numbers are the same size.
To measure something, put the 0 at one end. Then look at the number at the other end. That number tells you the length in centimetres.
Write each length in a table, with the name of the thing and its length. Then you can compare them later.
Key ideas
- Start measuring at 0.
- Read the number at the other end.
- cm means centimetres.
- Write the length with its unit, like 6 cm.
Method. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 0 cm
- Find where the line ends. Read the number at the other end.End: 4 cm
- Take the start away from the end. The length is the distance between the two numbers.4 − 0 = 4
- Write the answer. 4 cm
Check. Count along the ruler from 0 to 4: that is 4 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
Method. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 0 cm
- Find where the line ends. Read the number at the other end.End: 9 cm
- Take the start away from the end. The length is the distance between the two numbers.9 − 0 = 9
- Write the answer. 9 cm
Check. Count along the ruler from 0 to 9: that is 9 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
| Thing | Length |
|---|---|
| Pencil | 6 cm |
| Crayon | 4 cm |
| Ribbon | 9 cm |
Key words. Longest and tallest mean the biggest. Shortest means the smallest.
Method. Measure each one. The longest one has the biggest number.
- Measure each one. Count or read the length of each one.Pencil: 6 cm
Crayon: 4 cm
Ribbon: 9 cm - Find the biggest number. Compare the numbers, not the names.9 is the biggest number
- Write the answer. Ribbon is the longest one.
Check. The other ones have less than 9. ✓
Watch out. Look at every one before you choose. The first one you see is not always the answer.
Watch out
Watch out: many children start at the 1, not at the 0. If the pencil starts at 1, the number at its end is one too big. Start at 0.
Exam tip
Grown-up tip. Use a real ruler. Let your child lay it along a pencil, a book or a sock. Ask: “Where does it start? Where does it end?” Write each length on a sticky note with cm after it.
Exercise 7F Measuring in centimetres
Non-calculatorMethod. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 0 cm
- Find where the line ends. Read the number at the other end.End: 5 cm
- Take the start away from the end. The length is the distance between the two numbers.5 − 0 = 5
- Write the answer. 5 cm
Check. Count along the ruler from 0 to 5: that is 5 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
Method. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 0 cm
- Find where the line ends. Read the number at the other end.End: 8 cm
- Take the start away from the end. The length is the distance between the two numbers.8 − 0 = 8
- Write the answer. 8 cm
Check. Count along the ruler from 0 to 8: that is 8 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
Method. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 0 cm
- Find where the line ends. Read the number at the other end.End: 3 cm
- Take the start away from the end. The length is the distance between the two numbers.3 − 0 = 3
- Write the answer. 3 cm
Check. Count along the ruler from 0 to 3: that is 3 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
Method. Start each line at 0, then find the one that ends at 6.
- Read where each line ends. Every line starts at 0.A ends at 4
B ends at 6
C ends at 9 - Find the line that ends at 6. We want a line that is 6 cm long.B ends at 6
- Write the answer. B
Check. Count along the ruler from 0 to 6. ✓
Watch out. Look at the far end of each line, not the middle.
Key words. Longest and tallest mean the biggest. Shortest means the smallest.
Method. Measure each one. The longest one has the biggest number.
- Measure each one. Count or read the length of each one.A: 7 cm
B: 2 cm
C: 5 cm - Find the biggest number. Compare the numbers, not the names.7 is the biggest number
- Write the answer. A is the longest one.
Check. The other ones have less than 7. ✓
Watch out. Look at every one before you choose. The first one you see is not always the answer.
Key words. How much longer means the extra amount that one has.
Method. Line them up at the start. Count the extra part on the longer one.
- Measure Aisha. Count or read its length.Aisha: 7 cm
- Measure Tom. Count or read its length.Tom: 4 cm
- Find the extra part. Take the smaller number away from the bigger number.7 − 4 = 3
- Write the answer. 3 cm
Check. Check: 4 + 3 = 7. ✓
Watch out. Count only the extra part at the end of the longer one, not the whole of it.
Method. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 2 cm
- Find where the line ends. Read the number at the other end.End: 7 cm
- Take the start away from the end. The length is the distance between the two numbers.7 − 2 = 5
- Write the answer. 5 cm
Check. Count along the ruler from 2 to 7: that is 5 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
Method. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 0 cm
- Find where the line ends. Read the number at the other end.End: 3 cm
- Take the start away from the end. The length is the distance between the two numbers.3 − 0 = 3
- Write the answer. 3 cm
Check. Count along the ruler from 0 to 3: that is 3 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
Method. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 0 cm
- Find where the line ends. Read the number at the other end.End: 7 cm
- Take the start away from the end. The length is the distance between the two numbers.7 − 0 = 7
- Write the answer. 7 cm
Check. Count along the ruler from 0 to 7: that is 7 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
Method. Find the start and the end on the ruler. Then take the start away from the end.
- Find where the line starts. Put your finger on the start.Start: 0 cm
- Find where the line ends. Read the number at the other end.End: 5 cm
- Take the start away from the end. The length is the distance between the two numbers.5 − 0 = 5
- Write the answer. 5 cm
Check. Count along the ruler from 0 to 5: that is 5 centimetres. ✓
Watch out. Start at 0 when you can. If the line starts at 2, take 2 away from the end number.
| Thing | Length |
|---|---|
| Pencil | 5 cm |
| Crayon | 8 cm |
| Ribbon | 3 cm |
Key words. Longest and tallest mean the biggest. Shortest means the smallest.
Method. Measure each one. The shortest one has the smallest number.
- Measure each one. Count or read the length of each one.Pencil: 5 cm
Crayon: 8 cm
Ribbon: 3 cm - Find the smallest number. Compare the numbers, not the names.3 is the smallest number
- Write the answer. Ribbon is the shortest one.
Check. The other ones have more than 3. ✓
Watch out. Look at every one before you choose. The first one you see is not always the answer.
Method. Measure each one. Two of them match exactly, so they are the same length.
- Measure each one. Read or count the length of each one.A: 5 cm
B: 8 cm
C: 5 cm - Find the two that match. Things with the same length are the same length.A = 5, C = 5
- Write the answer. A and C
Check. Compare each pair to check. Only A and C match. ✓
Watch out. Measure, do not guess from the picture.