Multiplying Two Numbers Whose Difference is a Small Even Number

Here is mathematical trick to multiply any two number whose difference is an even number. Shortcut tricks are very helpful for fast calculations in competitive exams as time allotted is too less for lengthy calculations. So shortcut tricks helps us to solve questions is very less time hence improving chances of getting good score and higher rank in merit.

Multiplying Any Two Numbers Whose Difference is a Small Even Number

Follow steps below:

Find the number midway between two numbers. (Eg. 17 * 23. Number midway between 17 and 23 is 20).
Square this number. (20 * 20 = 400)
Halve the difference and square it. (23 - 17 = 6, 6/2 = 3, 3 * 3 = 9)
Now subtract it from result in step - 2 and this is your answer. (400 - 9 = 391)

Follow examples below to understand it better:

Eg. 1:

31 * 39
Step -1 => Number between 31 and 39 is 35.
Step -2 => 35 * 35 = 1225.
Step -3 => 8 / 2 = 4, 4 * 4 = 16
Step -4 => 1225 - 16 = 1209

Hence 31 * 39 = 1209. (Ans)

Eg. 2:

61 * 79
Step -1 => Number between 61 and 79 is 70
Step -2 => 70 * 70 = 4900
Step -3 => 18 / 2 = 9, 9 * 9 = 81
Step -4 => 4900 - 81 = 4819
Hence 61 * 79 = 4819. (Ans)

Try it yourself:

31 * 41 =

22 * 28 =

54 * 56 =

82 * 76 =

14 * 26 =

Mathematics is all about practice. Practice more and more problems of this type to improve your speed.

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