The idea in brief. A measurement needs a suitable unit, and a compound measurement records whole large units and the extra small units. Choose a unit that fits the object. Capacity is the most a container can hold, not how much it holds now. In the lesson. In Primary 2, you measured length in metres and centimetres, mass in kilograms and grams, and volume in litres. Today, we will choose suitable units and write measurements in two units. A measurement in two units gives the whole big units first, then the extra small units.
Lesson video, with the working
Choosing units and measuring in two units
6 min 00 s
The film teaches 3 questions in turn. Each question shows first; its working is written as the film explains it.
How do you answer choosing units of measurement questions in P3?
This page covers choosing a sensible unit (km, m or cm; kg or g; litres or ml) and writing a measurement in two units, such as 3 m 20 cm or 2 kg 150 g.
What your child learns here
This page covers choosing a sensible unit (km, m or cm; kg or g; litres or ml) and writing a measurement in two units, such as 3 m 20 cm or 2 kg 150 g. It follows the P3 outcomes on measuring length in kilometres, volume of liquid in millilitres, and measuring in compound units.
Choose km for long distances, m for rooms and buildings, and cm for small objects.
Choose g for light things like a letter, and kg for heavier ones like a bag of rice.
Choose ml for small amounts of liquid and litres for larger containers.
Write a compound measurement with the whole big units first, then the extra small units.
Tell capacity, the most a container can hold, apart from the volume of liquid in it now.
Does the answer make sense?
A measurement makes sense only if the number and unit together fit the object: a child's bicycle of 9 g would weigh less than a few coins. In your child's two-unit answer, the small part must be less than one big unit, so under 100 cm, 1000 g or 1000 ml.
How to practise these questions
The Basic questions practise choosing between units of length, mass and volume. The Intermediate questions add measuring and writing lengths or masses in two units, such as metres and centimetres. The Challenge questions ask your child to judge which unit or reading makes sense when the options are close. If choosing a unit stalls, play that question's solution film and try it again later from Revision.
Questions parents ask
Is kilometres taught in Primary 3? Yes. The Primary 3 MOE syllabus adds measuring length in kilometres and volume of liquid in millilitres, along with measuring length, mass and volume in compound units such as 2 km 300 m.
What is the difference between capacity and volume? Capacity is the most a container can hold. Volume of liquid is how much is in it at the moment. A 1-litre bottle has a capacity of 1 litre whether it is full, half-full or empty.
How can my child get a feel for units of measurement? Handle real objects: lift a 1 kg bag of sugar, pour a 1-litre carton into a jug, pace out 1 metre. With these benchmarks in mind, choosing between grams and kilograms, or metres and kilometres, becomes much easier.
