How_To_Be_Good_At_Math

Calculating with mass

Calculating

with mass

We can do calculations with mass in the same way

that we do with lengths and other measurements.

As long as the masses are in the same units, we can

simply add, subtract, multiply, or divide them.

Comparing mass with

mixed units

When you’re tackling a

problem that involves mass,

it’s important to pay attention

to the units. If the masses are

not all in the same unit, you’ll

need to start by doing some

conversion. We looked at

converting masses

on page 182.

Calculating mass with the same units

To work this out, we simply need to

add the three masses together:

85 + 73 + 94 = 252

Look at these three parrots. If we add

their masses together, what is their

total mass?

It might seem tricky at first

because their masses are

not in the same unit. To make it

easier, we’re going to do a

conversion.

Look at these three animals.

Can you put them in order,

from the heaviest to the lightest?

Let’s change the parrot’s

mass into kilograms so that

all the masses are in the same

unit – kilograms.

So, the parrots have a total mass

of 252 g.

TRY IT OUT

Weighing it up

Subtracting with mass is just as easy as adding.

Can you calculate how much heavier the yellow

toucan is than the green toucan? All you need to do

is subtract the smaller mass from the larger mass.

80 g

87 g

Answer on page 319

85 g 85 g

73 g

94 g

184_185_Calculating_with_mass.indd 184 29/02/2016 18:57