Basic Calculations

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Basic Calculations

• Common Percentages 1

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Finding 25, 50 and 75 of an amount
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In this lesson you will learn
To find a percentage of an amount using common
percentages 25, 50, 75
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We must remember what fraction each percentage
stands for
50 ½
25 ¼
75 ¾
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Example 1 Find 50 of 138
25 ¼ 50 ½ 75 ¾
Solution 50 of 138
½ of 138
138 ? 2
69
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Example 2 Find 25 of 33
25 ¼ 50 ½ 75 ¾
Solution 25 of 33
¼ of 33
33 ? 4
8?25
The next page shows the calculation without a
calculator
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Example 2 Find 25 of 33
25 ¼ 50 ½ 75 ¾
Note Because 33 does not divide exactly by 4,
we need to write 33?00 (pounds and pence) when
we are dividing
0
8
2
5
?
3
1
2
33?00
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Dont forget the decimal point in your answer!
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Example 3 Find 75 of 18 litres
25 ¼ 50 ½ 75 ¾
Solution 75 of 18 litres
Note Divide by 4 to find ¼
¾ of 18 litres
18 ? 4 ? 3 litres
Then Multiply by 3 to find ¾
13?5 litres
The next page shows the calculation without a
calculator
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Example 3 Find 75 of 18 litres
Note Because 18 litres does not divide exactly
by 4, we need to write 18?000 (add a few zeros)
when we are dividing
4?5
?
0
4
5
?3
1
2
4
18?000
?
5
13
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Dont forget the decimal point in your answer
Dont forget the decimal point in your answer
Notice we didnt need all the zeros this time
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You have learnt how to find 25, 50 and 75 of
an amount using equivalent fractions
50 ½
25 ¼
75 ¾
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