How_To_Be_Good_At_Math

MEASUREMENT • AREA MEASUREMENT • ESTIMATING AREA 169

Estimating area

Finding the areas of shapes that are not squares or rectangles

may seem tricky. But we can combine the number of completely full

squares and partly full squares to estimate the area.

We can estimate its area if we

draw a square grid over the pond,

where each square represents 1 m².

Most of the partial squares cover

just over or just under half a

square. So, to estimate the number

of squares they cover in total, we can

divide the number by 2: 26 ÷ 2 = 13

Look at this pond. Its unusual

shape makes it difficult to work

out its area.

First, we count all the squares

that are completely filled with

water by colouring them in. There

are 18 full squares.

Finally, we add together the

areas of the full squares and

the partially filled squares to get an

estimate of the total area: 18 + 13 = 31

Next, we count the squares that

are only partially filled by water.

There are 26 partially filled squares.

So, the area of the pond is

approximately 31 m².

Count the

squares that are

completely filled

with water

Count the

squares that are

partially filled

Each

square is

1 m along

each side

6 m

11 m

Ignore the squares

that aren’t

completely filled

Drawing a square grid over an

unusual shape can help us to

find its estimated area.

168_169_Area.indd 169 29/02/2016 18:03