Friday, July 12, 2013

Multiplication of numbers closer to 100 (part 2)

Multiplication of numbers closer to 100  (> 100)


Say, we want to multiply 104 x 113
                            
so,         104 --------4
              113--------13

step 2. multiply  4 x 13 and record as 52.

step 3. add 13 to 104 or 4 to 113, both will always be same.
so, we have 13 + 104 = 117, or 4 + 113  = 117
step 4. write the answer as 11752

Let us take another example
Say, we want to multiply 109 x 117

                         
so,         109 --------9
              117--------17

step 2. multiply  9 x 17 and record as 153.

step 3. add 17 to 109 or 9 to 117, both will always be same.
so, we have 17 + 109 = 126, or 9 + 117  = 126
step 4. write the answer as 1 2 6
                                +             1  5 3
                                          1 2 7 5 3              

note that if you have a 3 digit number in step 2, you will have to carry 1 in step 3.


Say, we want to multiply 109 x 116
multiply  9 x 16 = 144, the 1 has to be carried, so keep it in mind.
add 109 +16 mentally and write ---------125, add the carry 1, so you get 126.
write the answers as 12644
                         
Say, we want to multiply 112 x 115
multiply  12 x 15 = 180, the 1 has to be carried, so keep it in mind.
add 112 +15 mentally and write ---------127, add the carry 1, so you get 128.
write the answers as 12880

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