How_To_Be_Good_At_Math

MEASUREMENT • CALCULATING WITH LENGTH 163

Calculating with mixed units

We already know we can use different units

to record length. If you are calculating with

lengths, it is really important to make sure

the values are all in the same unit before

you start calculating.

The robot in this picture is

going to leave his house and

travel 760 m to the toy shop,

1.2 km to the playground, and

then 630 m to the zoo. How far

is the total journey?

2590 is quite a large

number, so converting it

back into kilometres will make it

a more sensible number. To do

this, we just need to divide by

1000: 2590 ÷ 1000 = 2.59

Now we can add all the

distances together because

they are all in metres:

760 + 1200 + 630 = 2590

First, we have to put all the

measurements into the

same units. So, we need to

change the distance between

the toy shop and the playground

from kilometres to metres.

Remember, to convert

kilometres to metres,

we just multiply the number

of kilometres by 1000, because

1 km is the same as 1000 m:

1.2 × 1000 = 1200

So, the robot will travel a

total distance of 2.59 km.

760 m 1.2 km 630 m

When calculating with distances,

make sure the measurements

are all in the same unit.

162_163_Calculating_lengths.indd 163 29/02/2016 18:03