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Mental Math #1 – 2 Digit Quick Multiplication Technique (Using Percentages)

This mental math technique if applied with certain types of 2 digit number with many digit number multiplication problems will get you calculating with lightning speed and accuracy. The basic idea is to convert the given 2 digit number to its corresponding percentage multiplied by 100.

Let’s understand this technique with an example:

Calculate – 75 X 44 using the method that first strikes your mind and keep note of the time you took.

 

Now, take a look at the mind map for solving this problem!

Mind Math #1 D1

First you change 75 to 75% X 100 and then to ¾ X 100, then multiplying 44 to ¾ gives you 33 and then multiplying it by 100 gives you your answer of 3300.

Try out:

75 X 88, 25 X 2200, 75 X 89

Alright, so I assume you got your initial steps right. So, let’s go a bit further.

Calculate – 76 X 44

For this you would first calculate 75 X 44 which you would now calculate in a jiffy, and then add 44 to the answer.

i.e. 75 X 44 +1 X 44 = 3300 + 44 = 3344

Now, Try out:

76 X 98, 76 X 35, 28 X 33, 26 X 88, 55 X 88, 85 X 88, 65 X 88, 64 X 88

For 55 X 88, as you may probably have guessed,

55 can be converted to 55% X 100 and then to 50% + 5% X 100

50% X 100 can be written as ½ X 100 and 5% X 100 as 50%/10 X 100 = 50% X 10, which means :

To calculate, first find the half of 88, i.e. 44 multiply by 100, and add to it 44 X 10.

i.e. 4400 + 440 = 4840.

For 65 X 88

65 gets to be 65% X 100 = (75% – 10%) X 100 and multiplying that with 88 gives:

6600 – 880 = 5720

For 64 X 88, you minus out 88 from your earlier result

i.e. 5720 – 88 = 5632