When teaching children to choose sensible units to measure:
- Give children practical experience of:
- using lots of a chosen unit to establish that measuring requires counting all the units, e.g. measuring the length of the table by laying 10cm rods along the table;
- using one uniform or standard unit to establish that you do not need the actual number of physical units but can use the one unit repeatedly, e.g. measuring the length of a table using one 10cm rod again and again
- using standard units and having a feel for the size of a unit
- using measures both in the mathematics lesson and in cross-curricular contexts.
- Develop children's confidence in using uniform and standard units as well as practising the skills of identifying suitable units and gaining a feel for the size of a unit. Children who can use a ruler but have no idea how long a metre is or what a metre is used for are unlikely to be able to use measures confidently.
- Allow children to follow a line of enquiry and make choices about equipment and units of measurement. Begin with uniform non-standard units to help them understand the need for standard units.
- Offer resources such as matchsticks, pencils, garden canes, boxes filled with sand, multilink cubes, cups and jugs as well as standard units of measure. These will consolidate discussions about how to choose something suitable to carry out a measurement. Suggest what uniform non-standard measure and what standard measure could be used to measure:
- the height of a table
- the width of a book
- the weight of a shoe.
- Use a range of activities such as:
- finding a selection of objects that could be measured in centimetres, metres and kilograms
- selecting a suitable label to match an object, for example, choosing from 2 metres, 2 centimetres, 2 litres and 2 kilograms to label a lemonade bottle
- giving a group of children a unit of measure, for example, litres, and challenging them to take photographs of things they can find around the school that they could measure using that unit
- sorting a set of objects according to a given criterion, for example, containers that hold less, more, or exactly one litre, and recording findings in a simple table.
Examples of containers which hold more, less or exactly one litre sorted into a table. The first column is labelled 'hold less than one litre' and contains images of a measuring jug marked up to five hundred millilitres, a measuring jug marked up to two hundred and fifty millilitres, a spoon and two small bottles. The second column is labelled 'hold one litre' and contains images of a measuring jug marked up to one thousand millilitres and a litre bottle. The third column is labelled 'hold more than one litre' and contains images of a large, unmarked jug, a bucket and a large bottle.
- Link suggesting sensible units to estimating and checking. For example, while asking children what units they would use to find the weight of a given object, also ask them to estimate how heavy they think it is and how they can check the accuracy of their estimate. Children don’t need to be afraid of getting an estimate wrong, so you can repeat this several times to help them begin to become more accurate with their estimates.
- Develop children's confidence with the approximate nature of measurement by asking questions such as:
- What is about 10cm long/tall/wide/deep?
- What will balance about 1kg?
- What holds about 1 litre?
- How tall do you think I am, roughly?
