How_To_Be_Good_At_Math

162 MEASUREMENT • CALCULATING WITH LENGTH

Calculating with length

Calculations with length measurements work just like

other calculations. You simply add, subtract, multiply, and divide

the numbers as you would usually.

To find the difference in height,

we need to subtract the

smaller number from the larger

number: 16.6 − 15.4 = 1.2

This tree is 16.6 m tall. Four years

ago, it was 15.4 m tall. How much

has it grown?

This means that the tree has

grown 1.2 m in four years.

TRY IT OUT

Share the distance

This running track is

200 m long. If the four

robots each ran the same

distance in a relay race,

how far will each robot

need to run to cover the

whole track?

Answer on page 319

To figure out the answer,

all you need to do is a

simple division calculation.

Let’s try a trickier problem.

We know the tree has

grown 1.2 m over four years,

but how much is that per year?

Just divide the length of

the track by the number of

robots sharing the distance.

To solve this problem, all

we need to do is divide the

amount it has grown by the

number of years: 1.2 ÷ 4 = 0.3

So, the tree grew

0.3 m each year.

Calculating with the same units

3 years Now

ago

2 years

ago

1 year

ago

4 years

ago

200m

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