Addition (+) is the reverse of subtraction (-).

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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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64 - 38 = 26 

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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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26 + 38 = 64

 

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 (×) is the reverse of division (÷).

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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.

​

For example, you may perform the following division:

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26 ÷ 2 = 13 

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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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13 × 2 = 26