How_To_Be_Good_At_Math

Calculating with money

Calculating with money

We calculate with money in just the same way as we calculate

with decimal numbers. We can learn to do this in our heads, using

what we know about numbers, or use written methods, like column

addition (see pages 86-87) and column subtraction (see pages 96-97).

Let’s add £26.49 and £34.63 using

column addition. We looked at how

to do column addition on pages 86-87.

First, we write one number above the other number.

Line up the decimal points, and put another

decimal point lined up below in the answer line.

Next, we work from right to left, adding

each of the digits. The answer is £61.12

£26.49 + £34.63 = £61.12

£26.49 + £34.63 =?

Line up the

decimal points

MEASUREMENT • CALCULATING WITH MONEY

So, £26.49 + £34.63 = £61.12

Round it up

Another way we can

calculate with money

is by rounding up or

down. Prices are often

close to a whole number

of pounds, so it’s simpler

to round the amount

up to work out the rough

total. Then we just have

to adjust the answer

at the end. Remember,

£1 is equal to 100p.

Adding amounts of money

£40 + £46 =?

£86 − 3p = £85.97

£40 + £46 = £86

£39.98 + £45.99 =?

£39.98 + £45.99 = £85.97

Let’s add £39.98 and £45.99

by rounding both numbers up

to the nearest whole pound.

First, we add 2p to £39.98 to get

£40 and add 1p to £45.99 to get

£46. So, we’ve added a total of 3p.

Next, we add the two amounts

together: £40 + £46 = £86

Finally, we just have to subtract

the 3p that we added on at the

start: £86 – 3p = £85.97

So, £39.98 + £45.99 = £85.97

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