Percentage Decrease Calculator Demonstration This resource provides animated

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Percentage – Decrease – Calculator – Demonstration This resource provides animated demonstrations of the

Percentage – Decrease – Calculator – Demonstration This resource provides animated demonstrations of the mathematical method. Check animations and delete slides not needed for your class.

÷ 2 How can we quickly find these percentages of 130? ÷ 4 ÷

÷ 2 How can we quickly find these percentages of 130? ÷ 4 ÷ 5 170 ÷ 10 50% 85 25% 42. 5 20% 34 10% 17 5% 1% 8. 5 1. 7 ÷ 2 ÷ 10

How many different methods can you think of? Find 35% of 300.

How many different methods can you think of? Find 35% of 300.

Odd one(s) out? Which words don’t belong in this list? Decrease Decline Less Fractionise

Odd one(s) out? Which words don’t belong in this list? Decrease Decline Less Fractionise Reduction Shrink Loss Discount Depreciate Contract

These shoes are normally £ 80 In the sale they are 35% off! How

These shoes are normally £ 80 In the sale they are 35% off! How much do the shoes cost now? 5% 10% 10% 4 8 8 £ 80 100% 65% 80 − 8 − 8 − 4 = 80 − 28 = £ 52 We can find 35% & subtract that from the original amount. 8

DEMO Decreasing by a Percentage Decrease 50 by 10% Find 10% = 5 Original

DEMO Decreasing by a Percentage Decrease 50 by 10% Find 10% = 5 Original − 10% 50 − 5 = 45

DEMO Decreasing by a Percentage Decrease 80 by 30% Find 30% × 3 10%

DEMO Decreasing by a Percentage Decrease 80 by 30% Find 30% × 3 10% = 8 30% = 24 Original − 30% 80 − 24 = 56

DEMO YOUR TURN Decreasing by a Percentage Decrease 80 by 30% Find 30% ×

DEMO YOUR TURN Decreasing by a Percentage Decrease 80 by 30% Find 30% × 3 Decrease 70 by 40% Find 40% 10% = 8 30% = 24 Original − 30% 80 − 24 = 56 × 4 10% = 7 40% = 28 Original − 40% 70 − 28 = 42

DEMO Decreasing by a Percentage Decrease 220 by 15% Find 15% + 10% =

DEMO Decreasing by a Percentage Decrease 220 by 15% Find 15% + 10% = 22 5% = 11 15% = 33 Original − 15% 220 − 33 = 187

DEMO Decreasing by a Percentage Decrease 40 by 45% Find 45% × 4 10%

DEMO Decreasing by a Percentage Decrease 40 by 45% Find 45% × 4 10% = 4 40% = 16 5% = 2 45% = 18 Original − 45% 40 − 18 = 22

DEMO YOUR TURN Decreasing by a Percentage Decrease 40 by 45% Find 45% ×

DEMO YOUR TURN Decreasing by a Percentage Decrease 40 by 45% Find 45% × 4 10% = 4 40% = 16 5% = 2 45% = 18 Original − 45% 40 − 18 = 22 Decrease 160 by 35% Find 35% × 3 10% = 16 30% = 48 5% = 8 35% = 56 Original − 35% 160 − 56 = 104

DEMO Decreasing by a Percentage Decrease 40 by 45% Find 45% × 4 10%

DEMO Decreasing by a Percentage Decrease 40 by 45% Find 45% × 4 10% = 4 40% = 16 5% = 2 45% = 18 a) Decrease 120 by 10% YOUR TURN 108 b) Decrease 80 by 15% 68 c) Decrease 160 by 45% 88 d) Decrease 400 by 21% 316 e) Decrease 700 by 6% 658 f) Decrease 90 by 43% 51. 3 g) Decrease 60 by 2. 5% 58. 5 Original − 45% 40 − 18 = 22

Using decimals to find a percentage of a quantity. 300% = 80 × 3

Using decimals to find a percentage of a quantity. 300% = 80 × 3 80 80 200% = 80 × 2 80 100% = 80 × 1 80 50% = 80 × 0. 5 40 80 80

Using decimals to find a percentage of a quantity. 100% = 90 × 1

Using decimals to find a percentage of a quantity. 100% = 90 × 1 90 50% = 90 × 0. 5 45 75% = 90 × 0. 75 67. 5 27% = 90 × 0. 27 24. 3

Use a decimal to calculate these percentages of quantities. 100% = 70 × 1

Use a decimal to calculate these percentages of quantities. 100% = 70 × 1 100% = 270 × 1 70 270 50% = 70 × 0. 5 75% = 270 × 0. 75 45 202. 5 20% = 70 × 0. 2 32% = 270 × 0. 32 14 86. 4 90% = 70 × 0. 9 63 35% of 70 = 24. 5 67% = 270 × 0. 67 180. 9 12. 5% of 270 = 33. 75

Decreasing using a Decimal Multiplier 0. 7 1 Decrease 90 by 30% 100% 30%

Decreasing using a Decimal Multiplier 0. 7 1 Decrease 90 by 30% 100% 30% 0. 3 90 × (1 − 0. 3) = 90 × 0. 7 = 63

Decreasing using a Decimal Multiplier 0. 85 1 Decrease 140 by 15% 100% 15%

Decreasing using a Decimal Multiplier 0. 85 1 Decrease 140 by 15% 100% 15% 0. 15 140 × (1 − 0. 15) = 140 × 0. 85 = 119

Decreasing using a Decimal Multiplier 0. 85 1 Decrease 140 by 15% 100% 15%

Decreasing using a Decimal Multiplier 0. 85 1 Decrease 140 by 15% 100% 15% 0. 15 140 × (1 − 0. 15) = 140 × 0. 85 = 119 a) Decrease 160 by 20% 128 e) Decrease 510 by 34% 336. 6 b) Decrease 280 by 70% 84 f) Decrease 230 by 81% 43. 7 c) Decrease 150 by 25% 112. 5 g) Decrease 270 by 5% 256. 5 d) Decrease 310 by 35% 201. 5 h) Decrease 350 by 3. 5% 337. 75

Questions? Comments? Suggestions? …or have you found a mistake!? Any feedback would be appreciated

Questions? Comments? Suggestions? …or have you found a mistake!? Any feedback would be appreciated . Please feel free to email: tom@goteachmaths. co. uk