Saturday 23 March 2013

Easy Multiplication of 5 digit numbers


Multiplication of two five digit numbers

Suppose we have to multiply two 5 digit numbers like

   3 5 4 1 2
x 2 6 3 4 1
--------------------------



To multiply these numbers take the first digits from left of both numbers, multiply them and put it for the right end of the result.

   3 5 4 1 2
x 2 6 3 4 1
--------------------------            3x2=6

6

Take the next 2 digits one by one also to the box and cross multiply the digits and add the sum and place it as the next digit of result.. push carry to the first digit just in case

   3 5 4 1 2
x 2 6 3 4 1
--------------------------       3x6 + 5x2 =18+10 =28
2
6 8

   3 5 4 1 2
x 2 6 3 4 1
--------------------------       3x3 + 4x2 + 5x6 = 9+8+30 =47
  2 4
 6 8 7

   3 5 4 1 2
x 2 6 3 4 1
--------------------------        3x4 + 1x2 + 5x3 +6x4 = 12+2+15+24 =53
2 4 5
6 8 7 3

   3 5 4 1 2
x 2 6 3 4 1
--------------------------        3x1 + 2x2 + 5x4 +6x1+ 4x3 = 3+4+20+6+12 = 45
2 4 5 4
6 8 7 3 5
 
   3 5 4 1 2
x 2 6 3 4 1
--------------------------         5x1 + 6x2 + 4x4 +3x1 = 5+12+16+3 = 36
2 4 5 4 3
6 8 7 3 5 6


  3 5 4 1 2
x2 6 3 4 1
--------------------------               4x1 + 3x2 + 4x1  = 4+6+4 = 14
2 4 5 4 3 1
6 8 7 3 5 6 4
 
  3 5 4 1 2
x2 6 3 4 1
--------------------------                     1x1 + 4x2  = 1+8 = 9
2 4 5 4 3 1
6 8 7 3 5 6 4 9
 
  3 5 4 1 2
x2 6 3 4 1
--------------------------                2x1  = 2
2 4 5 4 3 1
6 8 7 3 5 6 4 9 2
 
Now add the carry to get the answer
1  1 
2  4  5  4  3  1
6  8  7  3  5  6  4  9  2
---------------------------------
9  3  2  7  8  7  4  9  2
---------------------------------
 
so answer is 932787492
 
 
 


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