# Decimals

GCSELevel 1-3Cambridge iGCSEEdexcel iGCSE

## Decimals

A decimal is a number in between two whole numbers.

For example: the decimal $4.5$ is between the whole numbers $4$ and $5$

Decimals have numbers to the right of a decimal point.

All of these are examples of decimals: $3.6, 4.98, 8.546$

Make sure you are happy with the following topics before continuing:

## The Four Operations

We can use the four operations (addition, subtraction, multiplication and division) with decimals, and using our calculator, the method is the same.

Just as before, addition can be done by typing equations into your calculator, for example:

$4.6+5.9=10.5$

Subtraction:

Similarly to addition, we can use our calculator to work out subtraction questions, for example:

By typing in $13.8-11.1$, our calculator would give the solution, $2.7$.

Multiplication:

Again, we can use our calculator to work out multiplication questions:

If we had to multiply $3.7$ by $2.8$, we would type in $3.7\times2.8$, and the calculator would output $10.36$.

Division:

And finally, we can use our calculator to work out division questions, for example:

$60$ divided by $1.5$ would be calculated by typing in $60\div1.5$, giving the answer $40$.

As explained in The Four Operations, there may be simple operation questions, or more complicated, applied questions. These will be covered in the example questions.

Level 1-3GCSECambridge iGCSEEdexcel iGCSE

## Example 1: Simple Operations

Use your calculator to work out these four operation questions:

a) $1.35+1.6+1.89$

b) $100.5-6.8-5.99$

c) $2.1\times3.6\times4.5\times1.2$

d) $364\div3.5\div5.2$

[4 marks]

a) By typing the sum into a calculator:

$1.35+1.6+1.89=4.84$

b) By typing the sum into a calculator:

$100.5-6.8-5.99=87.71$

c) By typing the sum into a calculator:

$2.1\times3.6\times4.5\times1.2=40.824$

d) By typing the sum into a calculator:

$364\div3.5\div5.2=20$

Level 1-3GCSECambridge iGCSEEdexcel iGCSE

## Example 2: Applied Operations

Hugo is going to a supermarket. He buys broccoli for $\text{£}1.10$, a bag of carrots for $\text{£}0.89$ and $12$ potatoes each priced at $\text{£}0.38$.

By using multiplication and addition, calculate how much money Hugo spent overall at the supermarket.

[3 marks]

Firstly, we can work out how much he spent in total on potatoes by multiplying the price by the number of potatoes bought:

$\text{£}0.38\times12=\text{£}4.56$

Now, we can add up everything he bought to find his total:

$\text{£}4.56+\text{£}1.10+\text{£}0.89=\text{£}6.55$

Level 1-3GCSECambridge iGCSEEdexcel iGCSE

## Decimals Example Questions

We can solve this using addition on our calculator:

$\text{£}120.99+\text{£}5.99+\text{£}210.70=\text{£}337.68$

We can solve this problem using subtraction on our calculator:

$\text{£}10-\text{£}1.39-\text{£}1.20-\text{£}3.79=\text{£}3.62$

Pink doughnuts:

$6\times\text{£}0.79=\text{£}4.74$

Fizzy drinks:

$12\times\text{£}0.99=\text{£}11.88$

Bananas:

$3\times\text{£}0.99=\text{£}2.97$

$2\times\text{£}3.99=\text{£}7.98$

Total:

$\text{£}4.74+\text{£}11.88+\text{£}2.97+\text{£}7.98=\text{£}27.57$

We can divide this total by $3$ to see how much Ben spent:

$\text{£}27.57\div3=\text{£}9.19$

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