Functional Skills Mathematics
(Entry Level 3)
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Topic 4: Checking your answer


Addition (+) and subtraction (-) are inverse operations.
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This means that every addition is a subtraction in reverse, and every subtraction is an addition in reverse.
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3 + 2 = 5
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5 - 2 = 3
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Notice how the same three numbers are used, but in the reverse order. This fact is very useful for checking your answer when calculating.
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For example, you may perform the following subtraction:
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584 - 408 = 176
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To check that this is correct you can reverse the subtraction into an addition (which most people find easier than subtraction):
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176 + 408 = 584
If you end up with the same three numbers, but in reverse order, you can be confident your subtraction was correct.
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Multiplication (×) and division (÷) are inverse operations.
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This means that every multiplication is a division in reverse, and every division is a multiplication in reverse.
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5 × 2 = 10
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10 ÷ 2 = 5
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Notice how the same three numbers are used, but in the reverse order. This fact is very useful for checking your answer when calculating.
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For example, you may perform the following division:
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255 ÷ 3 = 85
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To check that this is correct you can reverse the division into a multiplication (which most people find easier than division):
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85 × 3 = 255
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