Grade 4 · Unit 5: Using units of measurement

Length and perimeter

Convert units and find perimeters.

A bamboo fence around a home garden.

Building a fence

A family wants a bamboo fence around their vegetable garden. They need to know the perimeter. They also need to convert between m and cm.

Converting units

To change to a smaller unit, multiply. 3.5 m = 350 cm. To change to a bigger unit, divide: 2500 m = 2.5 km.

Perimeter of rectangles

Perimeter of a rectangle = 2 × (length + width). 2 × (6 + 3) = 18 m. The family needs 18 m of fence.

Rectilinear shapes

For an L-shape, work out any missing sides. Then add all the sides. This L-shape has perimeter 5 + 2 + 3 + 2 + 2 + 4 = 18 units.

Decimals in measures

Measures are often written with decimals: 1.250 kg. To convert, multiply or divide by 10, 100 or 1000. Measure lines to the nearest millimetre: 4.6 cm = 46 mm.

What I learnt