 Percentages of Money Revision | KS3 Maths Resources

## What you need to know

Things to remember:

• We can find a percentage amount by breaking it up into smaller percentages and adding/subtracting/dividing, or by finding 1% and multiplying.
• When writing money, we write it to 2dp. So, we may need to add an extra decimal or round.

Before we start, it is worth remembering some simple percentage conversions:

Percentage Division

100% $\div1$

50% $\div2$

25% $\div4$

20% $\div5$

10% $\div10$

5% $\div20$

4% $\div25$

2% $\div50$

1% $\div100$

Finding percentage amounts of money is the same as finding amounts of just normal numbers, which we learn two methods for in Comparing Percentages.

What is 30% of £82?

We’ll use Method 1 from Comparing Percentages.

$$30\%=20\%+10\%$$

Step 2: Find the value of these percentages

$$20\%\text{ of }\pounds 82 = \pounds 82\div5=\pounds 16.4$$

$$10\%\text{ of } \pounds 82 = \pounds 82\div10=\pounds 8.2$$

$$30\%=20\%+10\%$$

$$30\%\text{ of } \pounds82=\pounds 16.4+\pounds 8.2=\pounds 24.6$$

But, we have to remember that when we have money it comes in 2dp, so the answer is £24.60.

What is 89.5% of £15?

We’ll use Method 2 from Comparing Percentages.

Step 1: Divide the number you’re finding the percentage of by 100 to find 1%.

$$15\div100=0.15$$

$$1\%=0.15$$

Step 2: Multiply the value of 1% found in Step 1 by your starting percentage.

$$89.5\%=89.5\times1\%$$

$$89.5\%\text{ of }15=89.5\times0.15=13.425$$

So, this time, our answer is £13.425. But, now we have too many decimal places, so we need to round it so we only have two. Our answer this time will be £13.43.

## Example Questions

Method 1

$$29\%=25\%+5\%-1\%$$

Step 2: Find the value of these percentages

$$25\%\text{ of }26=26\div4=6.5$$

$$5\%\text{ of }26=26\div20=1.3$$

$$1\%\text{ of }26=26\div100=0.26$$

$$29\%=25\%+5\%-1\%$$

$$29\%\text{ of }24=6.5+1.3-0.26=7.54$$

29% of £26 is £7.54.

Method 2

Step 1: Divide the number you’re finding the percentage of by 100 to find 1%.

$$26\div100=0.26$$

$$1\%=0.26$$

Step 2: Multiply the value of 1% found in Step 1 by your starting percentage.

$$29\%=29\times1\%$$

$$29\%\text{ of }26=29\times0.26=7.54$$

29% of £26 is £7.54.

Method 1

$$18\%=20\%-2\%$$

Step 2: Find the value of these percentages

$$20\%\text{ of }35=35\div5=7$$

$$2\%\text{ of }35=35\div50=0.7$$

$$18\%=20\%-2\%$$

$$18\%\text{ of }35=7-0.7=6.3$$

Hint: Remember, we have to have two decimal places.

18% of £35 is £6.30.

Method 2

Step 1: Divide the number you’re finding the percentage of by 100 to find 1%.

$$35\div100=0.35$$

$$1\%=0.35$$

Step 2: Multiply the value of 1% found in Step 1 by your starting percentage.

$$18\%=18\times1\%$$

$$18\%\text{ of }35=18\times0.35=6.3$$

Hint: Remember, we have to have two decimal places.

18% of £35 is £6.30.

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