Length
Length tells us how long, how tall or how far. There are two kinds of length questions: comparing and measuring.
Compare without numbers
Sometimes you don't need numbers to compare. Just hold two pencils next to each other and look:
- the longer one is on the left,
- the shorter one is on the right.
For two objects you cannot move (a tree and a house), you compare with your eyes.
Compare with body parts
When you cannot put two things next to each other, your body becomes a ruler:
- a hand-span (from thumb to little finger when stretched out),
- a foot length,
- a step.
"My desk is 6 hand-spans long, the table is 9 hand-spans long — so the table is longer." This works because your hand-span stays the same.
Measure with centimetres
Centimetres are the most common length units used in school. A centimetre is short — about the width of an adult finger. We write it as cm.
1 cm = the width of a small fingernail
10 cm = a hand
100 cm = a metre, about the height of a chair
A small ruler is usually 30 cm long. The big one in the classroom is often 1 metre.
Try it
- Find something about 10 cm long (a hand!).
- Find something about 30 cm long (a small ruler!).
- Find something about 1 metre long (a chair, a kitchen counter!).