How_To_Be_Good_At_Math

179

Calculating with

mixed units

Sometimes you will

have to do calculations

Using a protractor

different units. The

easiest way to do this

is to convert the units

so that they are all

The mean

MEASUREMENT • CAPACITY MEASUREMENT • VOLUME

Look at the fish tank

again. We know that it

has a capacity of 50 l, but it is

now holding some water. The

volume of the water is 10 l.

If a robot pours another

30 l of water into the

tank, what will the volume of

the water be now?

To work out this sum, we

simply have to add the

two amounts together:

10 + 30 = 40

This means that the

volume of the water in

the tank is now 40 l.

This bottle of juice has

a volume of 1.5 l. If you

drink 300 ml of the juice,

how much will be left in

the bottle?

Changing the units of

one of the amounts

makes the calculation

easier. Remember, to

change litres to millilitres

we multiply by 1000.

Let’s change the bottle’s

volume to millilitres:

1.5 x 1000 = 1500

Now the calculation

is simpler:

1500 – 300 = 1200

So, 1200 ml is

left in the bottle.

1500

500

1000

750

250

1250

1.5

0.5

1

0.75

0.25

1.25

VOLUME (litres)

50

40

30

20

10

0

Volume

Volume is a measure of how big something is in three dimensions.

Liquid volume is similar to capacity and is also measured in millilitres and

litres. Adding and subtracting liquid volumes works just like other calculations.

VOLUME (litres)

50

40

30

20

10

0

LITRES

MILLILITRES

Volume

is 50 l

Volume is 10 l

Volume is 40 l

178_179_Volume_and_Capacity.indd 179 29/02/2016 18:08