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Simple Multiplication Verification Method



How do you verify your multiplication? Here is a simple method.
Always reduce computations to a single digit.

   43  
 x 92o
 3956

Add  4 + 3 = 7
Add  9 + 2 = 11  then reduce to a single digit  1 +1 = 2
Multiply  2 x 7 = 14  then reduce to a single digit  1 + 4 = 5
Add 3+9+5+6 = 23  then reduce to a single digit  2 + 3 = 5
Both numbers (5) are equal, therefore multiplication is correct.

Another example

     
358
   x 4920

 176136

Add 3 + 5 + 8 = 16 then reduce to a single digit  1 + 6 = 7
Add 4 + 9 + 2 = 15 then reduce to a single digit  1 + 5 = 6
Multiply 7 x 6 = 42 then reduce to a single digit 4 + 2 = 6
Add 1+7+6+1+3+6 = 24 then reduce to a single digit 2 + 4 = 6
Both numbers (6) are equal, therefore multiplication is correct.

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