Percentages Worksheets

8/6/2019 Percentages Worksheets

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Colins Maths Revision Notes Colin Roberts 2008 - 2011Percentages, fractions and decimals

Percent means per hundred, or out of every hundred. So if you have a group of youngsters trying for a place in a team (football,hockey, air display team, fishing, whatever) and only 10% are successful, this means that only 10 out of a hundred get a place.

Put another way, the success rate is 10 or 0.1, now to express this as a percentage, multiply by a hundred; 10 x 100 = 10%100 100

If 25 are successful, this gives a success rate of 25 x 100 = 25% (cancel the 100s)100

If 6 apply, and 3 get a place, (3 out of 6) then as a percentage, this is 3 or 1 multiply by 100 to give; 1 x 100 = 50%6 2 2

The number it is out of is always on the bottom

Now, if 50 out of 100 young people enter a painting competition, we can say this is the same as;

50 = 25 or 5 or 1 multiply by 100 to give; 1 x 100 = 50%100 50 10 2 2

this cancelling down gives us what are called equivalent fractions.

So -25 = 5 or 1 and 1 multiply by 100 to give; 1 x 100 = 25% Now try the equivalent sheet100 20 4 4 4

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Colins Maths Revision Notes Colin Roberts 2008 - 2011Percentage Increases

A whole amount of anything is 100%

We saw with our earlier sheets that a percentage of an amount went something like this;50% of 20 is: 50 x 20 = 1 x 20 = 10

100 2

The important thing was the top of the fraction multiplies, the bottom divides

An increase means you have more than you started with, and this is how you do it;

Say you put 10 in a bank, for a year, and they pay you 10% interest -An easy way to do this is to say 10% is 10 or 0.1

100So your total amount is now 10 x 1.1 = 11

(If the interest had been 20%, your new amount would have been 10 x 1.2 = 12)

A different way would be to say 10% of 10 is 1 so your new amount is 10 plus 1 = 11

Now try these;

500ml + 25% 600ml + 50%

450Kg + 10% 450Kg + 30%



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Colins Maths Revision Notes Colin Roberts 2008 - 2011Percentage pattern forms

1) An item is 20, but has 10% off in the sale. What is the new price?

If the item is discounted, the selleris paying part of the cost, so youpay100% - discount. In this case, 100 10 = 90%

New Price = Old Price x 0.9

2) An item is 50 in sale, which is at 10% discount. What was the price before the sale?

This means OP x 0.9 = 50 so, OP = 50 0.9 or another way, 50

0.9

3) An item increases in price by 10% - this means it not only holds 100% of its price, but increases beyond it, in this case -NP = OP x 1.10

4) An item has an inflated price of 50, had an increase of 10%, what was the original price?

Original Pricex 1.10 = New (inflated Price)OP = NP

1.10

5) An item (often a car) is bought for say, 2000. it depreciates (loses value) at 5% per year how much is it worth after 3 years?

Year 1 - 2000 x 0.95 = 1900



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Colins Maths Revision Notes Colin Roberts 2008 - 2011Year 2 - 1900 x 0.95 = 1805Year 3 - 1805 x 0.95 = 1714.75

A quickway of doing this if you can remember it is;

2000 x (0.95)3 = 1714.75 where the amount in brackets is the depreciation, thepower is the number of years .

For savings interest, or an item increasing in value, appreciating, the rate becomes 1.05, 1.10, and so on.


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Percentages Worksheets