Percentage increase and decrease

The Maths Habit

Work out the percentage of the amount.

10% of 40100% = 404
20% of 30100% = 306
50% of 80100% = 8040

What has happened to bar A? What has happened to bar B?

StartBar A2 more pieces. It got bigger.Bar B3 pieces gone. It got smaller.

Increase
To make bigger.
100% = the whole+20%
Decrease
To make smaller.
100% = the whole−20%
The whole
All of the amount you start with. The whole is 100%.
the whole

Increase £50 by 20%.

100% = £50+20%555555555555120% = £60
1Find 10%.
50÷10=510%
2Find the change.
510%×2parts=1020%
3Add it on.
50100%+1020%=60120%

Increase £30 by 10%.

100% = £30+10%33333333333110% = £33
1Find 10%.
30÷10=310%
2Find the change.
310%×1parts=310%
3Add it on.
30100%+310%=33110%

Increase £50 by 20%.

100% = £50+20%555555555555120% = £60
1Find 10%.
50÷10=510%
2Find the change.
510%×2parts=1020%
3Add it on.
50100%+1020%=60120%
100% = amount+20%10%10%10%10%10%10%10%10%10%10%10%10%120% = answer1amount÷10=10%210%×parts=change3amount+change=answer

Increase £90 by 20%.

100% = £90+20%999999999999120% = £108
1Find 10%.
90÷10=910%
2Find the change.
910%×2parts=1820%
3Add it on.
90100%+1820%=108120%

Increase £50 by 20%.

100% = £50+20%555555555555120% = £60
1Find 10%.
50÷10=510%
2Find the change.
510%×2parts=1020%
3Add it on.
50100%+1020%=60120%
100% = amount+20%10%10%10%10%10%10%10%10%10%10%10%10%120% = answer1amount÷10=10%210%×parts=change3amount+change=answer

Increase £100 by 50%.

100% = £100+50%101010101010101010101010101010150% = £150
1Find 10%.
100÷10=1010%
2Find the change.
1010%×5parts=5050%
3Add it on.
100100%+5050%=150150%

Increase £50 by 20%.

100% = £50+20%555555555555120% = £60
1Find 10%.
50÷10=510%
2Find the change.
510%×2parts=1020%
3Add it on.
50100%+1020%=60120%
100% = amount+20%10%10%10%10%10%10%10%10%10%10%10%10%120% = answer1amount÷10=10%210%×parts=change3amount+change=answer

A plant is 30 cm tall. It grows by 50%. How tall is it now?

100% = 30 cm+50%333333333333333150% = 45 cm
1Find 10%.
30÷10=310%
2Find the change.
310%×5parts=1550%
3Add it on.
30100%+1550%=45150%

Add it on, or take it away?

  1. A price goes up by 20%.

    Add

  2. In a sale, the price goes down by 10%.

    Take away

  3. A puppy's weight increases by 50%.

    Add

  4. Decrease £40 by 20%.

    Take away

Decrease £60 by 20%.

100% = £60−20%666666666680% = £48
1Find 10%.
60÷10=610%
2Find the change.
610%×2parts=1220%
3Take it away.
60100%−1220%=4880%

Decrease £40 by 10%.

100% = £40−10%444444444490% = £36
1Find 10%.
40÷10=410%
2Find the change.
410%×1parts=410%
3Take it away.
40100%−410%=3690%

Decrease £60 by 20%.

100% = £60−20%666666666680% = £48
1Find 10%.
60÷10=610%
2Find the change.
610%×2parts=1220%
3Take it away.
60100%−1220%=4880%
100% = amount−20%10%10%10%10%10%10%10%10%10%10%80% = answer1amount÷10=10%210%×parts=change3amount−change=answer

Decrease £30 by 20%.

100% = £30−20%333333333380% = £24
1Find 10%.
30÷10=310%
2Find the change.
310%×2parts=620%
3Take it away.
30100%−620%=2480%

Decrease £60 by 20%.

100% = £60−20%666666666680% = £48
1Find 10%.
60÷10=610%
2Find the change.
610%×2parts=1220%
3Take it away.
60100%−1220%=4880%
100% = amount−20%10%10%10%10%10%10%10%10%10%10%80% = answer1amount÷10=10%210%×parts=change3amount−change=answer

Decrease £80 by 50%.

100% = £80−50%888888888850% = £40
1Find 10%.
80÷10=810%
2Find the change.
810%×5parts=4050%
3Take it away.
80100%−4050%=4050%

Decrease £60 by 20%.

100% = £60−20%666666666680% = £48
1Find 10%.
60÷10=610%
2Find the change.
610%×2parts=1220%
3Take it away.
60100%−1220%=4880%
100% = amount−20%10%10%10%10%10%10%10%10%10%10%80% = answer1amount÷10=10%210%×parts=change3amount−change=answer

A bike costs £80. In a sale, the price goes down by 10%. What is the sale price?

100% = £80−10%888888888890% = £72
1Find 10%.
80÷10=810%
2Find the change.
810%×1parts=810%
3Take it away.
80100%−810%=7290%

Percentage increase and decrease worksheet, page 1

Percentage increase and decrease worksheet, page 2

Answer sheet

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

  1. Increase 20 by 10%. Answer: 22

    Right

  2. Increase 40 by 20%. Answer: 60

    Wrong: add 20%, not 20

  3. Decrease 60 by 50%. Answer: 30

    Right

  4. Decrease 90 by 10%. Answer: 9

    Wrong: that is the change. Take it away.

  5. Decrease 100 by 20%. Answer: 80

    Right

  1. Increase £40 by 30%.

    £52

  2. Decrease £60 by 5%. Hint: 5% is half of 10%.

    £57

  3. Increase £80 by 25%.

    £100 (25% is a quarter, £20)

  4. A coat costs £80. Its price goes down by 50%. Then the new price goes up by 50%. Is it back to £80?

    No, it is £60

  5. Work out 50 × 1.2. Why is this the same as increasing 50 by 20%?

    60 (1.2 is 120%)

  1. Increase £70 by 20%.

    £84
    100% = £70+20%71Find 10%.70107÷=2Findthe change.×=3Addit on.+=

  2. Decrease £70 by 10%.

    £63
    100% = £70−10%1Find 10%.10÷=2Findthe change.×=3Takeit away.−=

  3. Increase £80 by 50%.

    £120
Exit tickets to print