Hi! I'm Vidi. Let's learn Measurement: Length together — read with me, then play the games to win a ⭐!
🔵Units of Length
We measure how long something is using units. From small to big:
- millimetre (mm) — very tiny, like the thickness of a coin.
- centimetre (cm) — your finger is about 1 cm wide.
- metre (m) — about the height of a door handle from the floor.
- kilometre (km) — a long distance you walk or drive.
We use a ruler to measure short lengths in cm and mm.
👀 See a worked example
Which unit best measures the length of a pencil?
Centimetres (cm) — a pencil is about 15 cm long.
Which unit best measures the distance between two cities?
Kilometres (km).
🤖 Vidi's Key Points
- Units of length from small to big: mm, cm, m, km.
- Use cm for small objects, m for a room, km for long distances.
- A ruler measures short lengths in centimetres and millimetres.
🟢Comparing & Converting Length
Useful conversions to remember:
- 1 cm = 10 mm
- 1 m = 100 cm
- 1 km = 1000 m
To change metres to centimetres, multiply by 100. To compare two lengths, make them the same unit first.
👀 See a worked example
How many centimetres in 3 metres?
3 × 100 = 300 cm.
Which is longer: 2 m or 150 cm?
2 m = 200 cm, and 200 cm > 150 cm, so 2 m is longer.
🤖 Vidi's Key Points
- 1 cm = 10 mm; 1 m = 100 cm; 1 km = 1000 m.
- Metres to centimetres: multiply by 100.
- To compare lengths, change them to the same unit first.
🎯 Mission Test
Ready, Maths Hero? Take the chapter test to show what you've learned!
Start the Chapter Test →