Length, Weight & Capacity — Class 3 IMO

Length: cm, m, km

Length is measured in centimetres (cm), metres (m) and kilometres (km). Short things are in cm, room-sized lengths in m, and long distances in km.

The key conversions are 1 m = 100 cm and 1 km = 1000 m. To change m to cm, multiply by 100; to change km to m, multiply by 1000.

Example 1: Change 2 m into centimetres.

2 × 100 = 200 cm.

Example 2: Change 3 km into metres.

3 × 1000 = 3000 m.

Quick recap

1 m = 100 cm; 1 km = 1000 m.
Use cm for small lengths, m for rooms, km for distances.

✓ Quick check

500 cm = ___ m?

500 ÷ 100 = 5 m.

1 km = ___ m?

1 km = 1000 m.

Weight (g, kg) & Capacity (ml, L)

Weight is measured in grams (g) and kilograms (kg), with 1 kg = 1000 g. Capacity (how much liquid a container holds) is measured in millilitres (ml) and litres (L), with 1 L = 1000 ml.

To change kg to g or L to ml, multiply by 1000; to go the other way, divide by 1000.

Example 1: Change 2 kg into grams.

2 × 1000 = 2000 g.

Example 2: Change 3 L into millilitres.

3 × 1000 = 3000 ml.

Quick recap

1 kg = 1000 g; 1 L = 1000 ml.
Bigger unit to smaller: multiply by 1000.

✓ Quick check

1 kg = ___ g?

1 kg = 1000 g.

2 L = ___ ml?

2 × 1000 = 2000 ml.

Adding, Subtracting & Word Problems

We can add or subtract measurements when they are in the same unit. For example, 250 ml + 350 ml = 600 ml, and 5 kg − 2 kg = 3 kg.

In word problems, words like in all and total mean add, while left and how much more mean subtract.

Example 1: Add 4 m 50 cm + 2 m 30 cm.

Add metres and cm separately: 6 m 80 cm.

Example 2: A bottle holds 1 L. You drink 250 ml. How much is left?

1 L = 1000 ml; 1000 − 250 = 750 ml left.

Quick recap

Add or subtract only when units are the same.
Convert first if the units are different.

✓ Quick check

250 ml + 350 ml = ?

250 + 350 = 600 ml.

750 g + 250 g = ?

750 + 250 = 1000 g, which is 1 kg.