You can use percentages to describe a change in a quality. It could be an increase or a decrease. A percetage change is always calculated as a percentage of the initial value. The initial value is 100%. It is important to choose the correct value to be 100%
Worked Example :
In May 800 people visited a museum. In June 900 People visited. In July, the number was 800 again. Work out:
a) the percentage increase from May to June
b) the percentage decrease from June to July
a) 100% = 800
The increase is 100. The percentage is increase is 100/800 x 100 = 12.5%
b) 100% = 900
The decrease is 100. The percentage decrease is 100/800 x 100 = 11.1%
Exercise 1:
Here are the prices of three items in Alain's shop.
a) Game $40
b) Phone $120
c) Computer $500
Alain increase all the prices by $10. Find the percentage increase for each item.
Exercise 2:
"The price after the sale is $20000 again"
The price of a car was $20000. In a sale, the price decreased by 4% After the sale it increased by 4%
a) what mistake has Ahmad made?
b) What is the correct price after the sale?
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