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History Of Math

Addition

Subtraction

Multiplication

Division

Number Notation

Multiplication Table

Divisibility Rules

Addition   -an operation of finding a sum of some numbers: 21 + 5 = 26. Here 21 and 5 – addends,  26 – the sum. If addends are changed by places, a sum is saved the same: 21 + 5 = 26 and 5 + 21 = 26. Math tricks 1: Adding by breaking apart a number Example: 137+85 =(122+15)+85 =122+100 =222 In example here,break 137 to 122 and 15. Math tricks 2: Adding by overadding Example: 247+97 =247+(100-3) =347-3 =344 In example here,97 was add to 100 first. Easy way to check your answer: Estimating the answer by rounding off numbers Example: 249 159 + 504 = 912 249 rounds off to 250,159 to 160 and 504 to 500,then add up these figures. 250 160 + 500 = 910 The amount that has been estimated is 910,so the answer should be around 910.If your answer is only 800,then you know it is wrong.

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