A quick way to multiply two numbers mentally

Can you multiply 104 by 103 within 5 seconds

Surprising!

Here is the trick

104 - 4 (here we consider 100 as the base and 104 is 4 more than 100)

103 - 3 (here we consider 100 as the base and 103 is 3 more than 100)

Step 1: Select any number and add the unit digit of the other number

Here add either  3 to 104 or 4 to 103; you get the first part of the answer i.e. 107

Step 2: Now multiply 4*3 you get the second part of the answer i.e. 12

so your answer is 10712

Now let's consider another example

107*108 

107 - 7 (here we consider 100 as the base and 107 is 7 more than 100)

108 - 8 (here we consider 100 as the base and 108 is 8 more than 100)

Step 1: Now  add either  7 to 108 or 8 to 107 ; you get the first part of the answer i.e. 115

Step 2: Now multiply 7*8; you get the second part of the answer i.e. 56 

so your answer is 11556