The note
How schools teach it now
Children learn the key facts (10 mm = 1 cm, 100 cm = 1 m, 1,000 m = 1 km, 1,000 g = 1 kg, 1,000 ml = 1 l) and convert by multiplying or dividing by 10, 100 or 1,000. Year 6 adds rough imperial links, e.g. 5 miles ≈ 8 km.
5-minute kitchen-table activity
Read labels in the cupboard: a 1.5 l bottle, a 750 g bag of rice, a 330 ml can. Convert each one (1,500 ml, 0.75 kg, 0.33 l). About how many cans would fill the bottle? (About four and a half.)
Worked example
A jug holds 1.2 litres. Mia pours out three glasses of 250 ml. How much is left?
- Change to millilitres: 1.2 l = 1,200 ml.
- Three glasses: 3 × 250 ml = 750 ml.
- 1,200 − 750 = 450.
Answer: 450 ml
Common mistakes to watch for
- Mixing units in one calculation without converting.
- Multiplying when they should divide (2,500 g is 2.5 kg).
- Thinking 1.2 l is 1,020 ml or 120 ml.
Encouragement
- Try saying
- “Is that a sensible size? Let's check it.”
- Rather than
- “You always get these wrong.”