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.

Step 1: Think about the percentages that add or multiply together to make your percentage.

 

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

Step 3: Add/Subtract/Multiply

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.

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Example Questions

Method 1

 

Step 1: Think about the percentages that add or multiply together to make your percentage.

 

 

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

 

Step 3: Add/Subtract/Multiply

 

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

 

Step 1: Think about the percentages that add or multiply together to make your percentage.

 

 

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

 

Step 3: Add/Subtract/Multiply

 

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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