Maths: the three basic percentages

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Type 1 find x% of y

1) find 10% of y by dividing it by ten. (You can easily do this by moving the decimal one place to the left.)

2) now you have 10% you can times it to find 20, 30 etc or half it to find 5.

3) Another way to do this is dividing the % you're given to find by 100 and times it by the numerical value you were given to find the % of.

Example : find 15% of £46
0.15 X 46 = 690 in pounds = £6.90

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Type 2 Find the new amount after a % increase/decr

1) Find the numerical % value - use the methods shown in type 1.
2) Whatever was the % given out of step 1 if the question is the new amount after a % increase add the answer in step 1 to the original value however, if it's a decrease take the answer in step 1 away from the original value.

Put into practise: A toaster is reduced in price by 40% in the sales. It originally cost £68. what is the new price of the toaster.
1) 40% of £68 = £27.2 method 1 = 10% of 68 = 6.8 to find 40% X that by 4 = £27.2.
Method 2: 0.4 X 68 = £27.2
2) Because the % of £68 = £27.2 and the question is a reduction question take it away from the original value £68 - £27.2 = £40.2

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Type 3 - "Express x as a % of y"

1) Make sure both of the numbers are in the same unit of measurement.
2) Divide the number that will be given as a percentage by the number it will give a percentage of and then times it by 100. Divide X by Y and then TMES by 100.

Put into practise: Give 40p as a percentage of £3.34
1) covert £3.34 into pence divide by 100.
2) 40/334 X 100 =12% (1.d.p)

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