Presentation on theme: "Reverse Percentages Finding the original price after deduction or increase Let’s do the first one together: A radio sells for £63, after a 40% increase."— Presentation transcript:
1Reverse PercentagesFinding the original price after deduction or increaseLet’s do the first one together:A radio sells for £63, after a 40% increase in the cost price. Find the cost price.
2Reverse PercentagesA radio sells for £63, after a 40% increase in the cost price. Find the cost price.The selling price is 100% + 40%, so £63 = 140%.Calculate 1%140% = £631% = £63/1401% = £0.45The cost price is 100%, so multiply £0.45 by 100Cost price = 0.45 x 100 = £45
3Another exampleA packet of washing powder is advertised as having '20% extra powder'. If it contains 1.32kg. What would the original pack contain?1.02kg?1.1kg?1.06kg?1kg?
4Another exampleA new car falls in value by 30% in a year. After a year, it is worth £8,400. Find the price of the car when it was new.Remember that the original price of the car is 100%.Original price = 100%.Second-hand price = 100% - 30% = 70%.So £8,400 = 70% of the original price.So 1% of original price = £8,400 ÷ 70Original price = 100% = 100 x 1% = 100 x (£8,400 ÷ 70)= £12,000.
5Footballers £ listingThe Association of Football has decided to re-price some of their footballers depending on their previous performance. Here are some of the new prices and their percentage increase or decrease:Ronaldo 113.4m INCREASE 40%Messi 160m DECREASE 20%Di Maria 71.88m INCREASE 19.8%Van Persie 18.75m DECREASE 25%Neymar 57.5m INCREASE 9.8%Falcao 40m INCREASE 5%Can you work out any 3-6 players’ original prices before the re-pricing?