Question

Tim buys a torch and a battery.

The torch costs eleven times as much as the battery.

Tim pays with a £10 note and gets £4.84 change.

How much does the battery cost?

(please show working out)

Answer 1

For this case, the first thing we must do is define variables.

We have then:

t: cost of the torch

b: cost of the battery

The cost of both items in £ is given by:

`10-4.84 = 5.16`

Therefore, we have the following equation:

`t + b = 5.16`

Then, we know that:

The torch costs eleven times as much as the battery.

`t = 11b`

Substituting equation two in the equation we have:

`11b + b = 5.16`

Clearing the value of b we have:

`12b = 5.16`

`b = (5.16)/(12)`

`b = 0.43`

Answer:

The cost of the battery is 0.43 £