Class 2 length: measuring and comparing in centimetres and metres
Length is the first measurement topic where a child picks up a real tool — the ruler — and reads a number off it. In Class 2 they measure in centimetres and metres, compare what is longer or shorter, and start to estimate before they measure.
The skill that trips children up is reading the ruler itself: lining the object up against the zero mark, and counting the little lines carefully. Get that right and the arithmetic of length is simple addition and subtraction.
What your child needs to know
- Measure a length in centimetres using a ruler
- Line an object up with the zero mark and read the end
- Know that 1 metre is the same as 100 centimetres
- Compare two lengths and say which is longer or shorter
- Add and subtract lengths in centimetres
Worked examples
A pencil is 12 cm and a crayon is 8 cm. How much longer is the pencil?
Hint — "how much longer" means take one length away from the other.
12 cm − 8 cm = 4 cm. The pencil is 4 centimetres longer than the crayon.
A ribbon is placed on a ruler from the 0 mark to the 9 mark. How long is it?
Hint — the length is the number the ribbon ends on when it starts at 0.
Starting at 0 and ending at 9, the ribbon covers 9 centimetres. It is 9 cm long. Always check the object starts exactly at 0, not at 1.
Which is longer, 1 metre or 90 centimetres?
Hint — change the metre into centimetres so both are in the same unit.
1 metre is 100 cm. Since 100 cm is more than 90 cm, 1 metre is longer.
A sunflower is 6 cm tall. It grows 3 cm, then 2 cm more. How tall now?
Hint — add each bit of growth to the height.
6 cm + 3 cm + 2 cm = 11 cm. This is exactly the kind of two-step growing our free Sunflower Garden game is built around.
How Olympiads test this
Olympiads such as SOF IMO and CREST CMO at Class 2 like ruler-reading pictures, "which is longest / shortest" comparisons, and simple length sums in centimetres. They may also ask which unit suits an object — centimetres for a pencil, metres for a room. Measuring real things around the house is the best practice; it builds the number sense no exam question can be predicted from.
Practice questions
Show 5 practice questions and answers
- A straw is 15 cm. You cut off 5 cm. How long is it now? — 10 cm
- How many centimetres are there in 1 metre? — 100 cm
- Which is shorter, 45 cm or 54 cm? — 45 cm
- A pencil is 13 cm and an eraser is 4 cm. Placed end to end, how long? — 17 cm
- A ribbon runs from 0 to 7 on a ruler. How long is it? — 7 cm
Inside Talyzo: World 5, Garden
Length is World 5, set in a garden — and it is the one topic you can try as a free game right now. In The Magic Sunflower Garden your child grows a sunflower to exactly the right height in centimetres, counting the lines on the ruler and planning two steps ahead. No signup, no download.
Free account, no card required.
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