Liri spread out her notes: distances, the weight of her cargo, how much drinking water was left, how many days the journey would still take, and how much her collected star gold was worth.
Before you measure, it is worth estimating. That sharpens your feeling for which unit makes sense in the first place.
🎲 Game idea: find an object that you think weighs exactly 500 g – and then weigh it. Whoever gets closest wins!
Millimetres (mm) for very small distances, centimetres (cm) and metres (m) for everyday things, kilometres (km) for long journeys. In between there is also the decimetre (dm) – each unit is exactly ten times as big as the one before.
| Unit | Conversion |
|---|---|
| 1 cm | = 10 mm |
| 1 dm | = 10 cm |
| 1 m | = 10 dm = 100 cm |
| 1 km | = 1000 m |
Grams (g) for light things (an egg weighs about 60 g), kilograms (kg) for larger amounts (a bag of flour weighs 1 kg).
| Unit | Conversion |
|---|---|
| 1 kg | = 1000 g |
New in Grade 3: millilitres (ml) for small amounts (a small juice carton holds 200 ml), litres (l) for larger ones (a bucket holds 10 l).
The fuller the measuring jug, the more millilitres – with a whole litre it is full to the brim with 1000 ml.
| Unit | Conversion |
|---|---|
| 1 l | = 1000 ml |
New: seconds (s). Time works differently from the other measures – not in tens, but in steps of 60!
| Unit | Conversion |
|---|---|
| 1 min | = 60 s |
| 1 h | = 60 min |
| 1 week | = 7 days |
| 1 year | = 12 months |
Calculating with amounts of money up to €1,000, and handling the decimal point with confidence: €2.50 = €2 and 50c.
When converting, zeros are often added or crossed out wrongly. A place value chart helps: write the lengths in columns one under the other.
3 m and 5 cm is not 3.5 m (that would be 3 m 50 cm) – it is 3.05 m! The chart shows straight away where the missing zero belongs.
A recipe needs 500 ml of milk. But Liri’s measuring jug only shows litres. Where does she have to pour to?
Training begins at 15:45 and lasts 50 minutes. When does it finish?
Jump in 10-minute steps up to the full hour, then carry on – training ends at 16:35.
The Moon is about 384,000 km away from the Earth.
An astronaut in space drinks about 2,000 ml (2 litres) of water a day – measured exactly, because nothing may be wasted.
A rocket often weighs several hundred thousand kg at launch – by far the largest part of that is fuel.
With the decimal point the zero is often forgotten: 1 kg 50 g is 1.050 kg, not 1.5 kg (that would be 500 g)!
Tip: use the place value chart – there you can see straight away how many zeros really belong.
Liri rewrote her travel notes: the distance in km, the weight of her cargo in kg, her water supply in litres, the remaining time in hours, and her collected star gold in euros.
Liri can now estimate, measure and safely convert in all five areas of measurement.