Reverse percentages

The Maths Habit

Work out the percentage of the amount.

10% of 60100% = 606
20% of 40100% = 408
50% of 30100% = 3015

This is part of a bar of chocolate. What does the whole bar look like?

Half a barDouble it: 10 pieces.A quarter of a bar4 lots of it: 8 pieces.

The whole
All of the amount. The whole is 100%.
the whole
A part
Some of the whole. The part you know is pink.
100% =?20% = part10%10%10%10%10%10%10%10%10%10%
Reverse
Work backwards: from the part to the whole.
100% =whole20% = part10%10%10%10%10%10%10%10%10%10%

10% is given. What is 100%?

10% = 4100% =?4010% = 44444444444100% = 40
10% = 9100% =?9010% = 99999999999100% = 90
10% = 12100% =?12010% = 1212121212121212121212100% = 120

20% of an amount is £8. Find the amount.

100% =?£4020% = £84444444444
1Find 10%.
820%÷2parts=410%
2Find 100%.
410%×10=40100%

20% of an amount is £6. Find the amount.

100% =?£3020% = £63333333333
1Find 10%.
620%÷2parts=310%
2Find 100%.
310%×10=30100%

20% of an amount is £8. Find the amount.

100% =?£4020% = £84444444444
1Find 10%.
820%÷2parts=410%
2Find 100%.
410%×10=40100%
100% =?20% = part10%10%10%10%10%10%10%10%10%10%1part÷parts=10%210%×10=100%

20% of an amount is £10. Find the amount.

100% =?£5020% = £105555555555
1Find 10%.
1020%÷2parts=510%
2Find 100%.
510%×10=50100%

20% of an amount is £8. Find the amount.

100% =?£4020% = £84444444444
1Find 10%.
820%÷2parts=410%
2Find 100%.
410%×10=40100%
100% =?20% = part10%10%10%10%10%10%10%10%10%10%1part÷parts=10%210%×10=100%

20% of an amount is £16. Find the amount.

100% =?£8020% = £168888888888
1Find 10%.
1620%÷2parts=810%
2Find 100%.
810%×10=80100%

20% of an amount is £8. Find the amount.

100% =?£4020% = £84444444444
1Find 10%.
820%÷2parts=410%
2Find 100%.
410%×10=40100%
100% =?20% = part10%10%10%10%10%10%10%10%10%10%1part÷parts=10%210%×10=100%

Sam has saved £18. This is 20% of the price of a bike. How much does the bike cost?

100% =?£9020% = £189999999999
1Find 10%.
1820%÷2parts=910%
2Find 100%.
910%×10=90100%

How many pink parts? What do you divide by?

  1. The part is 20%.

    100% =?20% = partDivide by 2

  2. The part is 50%.

    100% =?50% = partDivide by 5

  3. The part is 10%.

    100% =?10% = partDivide by 1

  4. The part is 30%.

    100% =?30% = partDivide by 3

50% of an amount is £20. Find the amount.

100% =?£4050% = £204444444444
1Find 10%.
2050%÷5parts=410%
2Find 100%.
410%×10=40100%

50% of an amount is £10. Find the amount.

100% =?£2050% = £102222222222
1Find 10%.
1050%÷5parts=210%
2Find 100%.
210%×10=20100%

50% of an amount is £20. Find the amount.

100% =?£4050% = £204444444444
1Find 10%.
2050%÷5parts=410%
2Find 100%.
410%×10=40100%
100% =?20% = part10%10%10%10%10%10%10%10%10%10%1part÷parts=10%210%×10=100%

50% of an amount is £25. Find the amount.

100% =?£5050% = £255555555555
1Find 10%.
2550%÷5parts=510%
2Find 100%.
510%×10=50100%

50% of an amount is £20. Find the amount.

100% =?£4050% = £204444444444
1Find 10%.
2050%÷5parts=410%
2Find 100%.
410%×10=40100%
100% =?20% = part10%10%10%10%10%10%10%10%10%10%1part÷parts=10%210%×10=100%

50% of an amount is £50. Find the amount.

100% =?£10050% = £5010101010101010101010
1Find 10%.
5050%÷5parts=1010%
2Find 100%.
1010%×10=100100%

50% of an amount is £20. Find the amount.

100% =?£4050% = £204444444444
1Find 10%.
2050%÷5parts=410%
2Find 100%.
410%×10=40100%
100% =?20% = part10%10%10%10%10%10%10%10%10%10%1part÷parts=10%210%×10=100%

Jo has read 45 pages. This is 50% of her book. How many pages are in the book?

100% =?90 pages50% = 45 pages9999999999
1Find 10%.
4550%÷5parts=910%
2Find 100%.
910%×10=90100%

Reverse percentages worksheet, page 1

Reverse percentages worksheet, page 2

Answer sheet

Is it right?
Thumbs up: right. Thumbs down: wrong.

  1. 10% is £8. So 100% is £80.

    Right

  2. 20% is £84. So 100% is £840.

    Wrong: 10% is 42, so £420

  3. 50% is £100. So 100% is £200.

    Right

  4. 20% is £44. So 100% is £220.

    Right

  5. 20% is £2. So 100% is £20.

    Wrong: 10% is 1, so £10

  1. 25% of an amount is £9. Find the amount. Hint: four lots of 25% make 100%.

    £36

  2. 5% of an amount is £3. Find the amount. Hint: 5% is half of 10%.

    £60

  3. A price goes up by 10%. It is now £66. What was it before? Hint: £66 is 110%.

    £60 (£66 is 110%)

  4. In a sale, a coat is 10% off. It now costs £45. What did it cost before?

    £50 (£45 is 90%)

  5. After a 20% increase, a price is £60. Find the price before.

    £50 (£60 is 120%)

  1. 20% is £24. Find 100%.

    £120
    100% =?20% = £24121Find 10%.24212÷=2Find 100%.10×=

  2. 50% is £30. Find 100%.

    £60
    100% =?50% = £301Find 10%.÷=2Find 100%.10×=

  3. 20% of an amount is £42. Find 100%.

    £210
Exit tickets to print