- Choose the right unit for length, mass and capacity
- Convert units: 1 m = 100 cm, 1 km = 1000 m, 1 kg = 1000 g, 1 l = 1000 ml
- Add and compare measurements in the same unit
How tall are you? How heavy is your school bag? How much water fits in a bottle? To answer these questions we measure: with a ruler, with scales and with a measuring jug.
Length
We measure short things in centimetres (cm): a school ruler is often 20 or 30 cm long. Tiny things are measured in millimetres (mm): an ant is only a few millimetres long. Longer things are measured in metres (m): a classroom door is about 2 m high. Long distances are measured in kilometres (km).
| What we measure | Units | How they are linked |
|---|---|---|
| Length | mm, cm, m, km | 1 cm = 10 mm, 1 m = 100 cm, 1 km = 1000 m |
| Mass | g, kg | 1 kg = 1000 g |
| Capacity | ml, l | 1 l = 1000 ml |
a) Leyla is 1 m 32 cm tall. How many centimetres is that?
b) Elvin jumped 245 cm in the long jump. Write this in metres and centimetres.
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b) 245 cm = 200 cm + 45 cm = 2 m 45 cm.
Mass
How heavy something is, its mass, is measured with scales in grams (g) and kilograms (kg). A bag of sugar often weighs 1 kg, while one sugar cube weighs only a few grams.
At the market Grandma bought 2 kg of apples and 500 g of cherries. How many grams is that altogether?
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2000 g + 500 g = 2500 g, that is 2 kg 500 g.
Capacity
How much liquid fits into a container is measured in litres (l). Small amounts are measured in millilitres (ml): a teaspoon holds about 5 ml. 1 l = 1000 ml.
A bucket holds 10 l of water. How many times do you need to pour from a 2-litre jug to fill it?
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You need to pour 5 times.
Let's practise
Each sum is a measuring question: for example, 3 × 100 finds how many centimetres there are in 3 metres.
- 1.3 × 100 =
- 2.100 + 45 =
- 3.2 × 1000 =
- 4.1000 − 300 =
- 5.10 ÷ 2 =
- 6.5 × 10 =
- 7.1000 − 250 =
- 8.3 × 1000 =
Key points
- Length: 1 cm = 10 mm, 1 m = 100 cm, 1 km = 1000 m.
- Mass: 1 kg = 1000 g.
- Capacity: 1 l = 1000 ml.
- Kilo means a thousand, centi a hundredth and milli a thousandth.
- Change to the same unit before adding or comparing.
Check yourself
10 questions. Every correct answer earns XP.