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Friday, 16 March 2012

IBPS MATHEMATICS | SSC MATHEMATICS | CHAPTER 2 MULTIPLICATION

SHORTCUT METHOD FOR MULTIPLICATION:

Multiplication by 11

The last digit of the multiplicand (the number multiplied) is put down as the right hand figure of the answer.
Each successive digit of the multiplicand is added to its neighbor at the right.

Example:

5892 X 11 =?
Change it to 05892 x 11=?

Step 1: put down last digit of 05892
                                05892 x 11=_ _ _ _ 2
Step 2: Each successive digit of 05892 is added to its neighbor at the right. That is

               9+2=11, write 1 and carry over 1 to next.
                05892 x 11=_ _ _ 1 2        carry 1

                8+9= 17 + carry = 17 +1 = 18. Write 8 and carry over 1.
                05892 x 11=_ _ 8 1 2        carry 1

                5+8= 13 + carry = 13 +1 = 14. Write 4 and carry over 1.
                05892 x 11=_ 4 8 1 2         carry 1.

                0+5= 5 + carry = 5 +1 = 6. Write 6
                05892 x 11=6 4 8 1 2         carry 0.

Multiplication by 12

Double the last digit of multiplicand and write as the right hand figure of the answer
Double Each successive digit of the multiplicand is added to its neighbor at the right.

Example:

5892 X 12 =?
Change it to 05892 x 12=?

Step 1: put down double of last digit of 05892
                                05892 x 11=_ _ _ _ 4
Step 2: double Each successive digit of 05892 is added to its neighbor at the right. That is
               9*2+2=20, write 0
               05892 x 12=_ _ _ 0 4        carry 2

               8*2+9+ carry = 25 + carry = 25 +2 = 27. Write 7 and carry over 2.
               05892 x 12=_ _ 7 0 4        carry 2

                5*2+8 + carry= 18 + carry = 18 +2 = 20. Write 0 and carry over 2.
                05892 x 12=_ 0 7 0 4         carry 2

                0*2+5 + carry= 5 + carry = 5 +2 = 7. Write 7
                05892 x 12=7 0 7 0 4         carry 0

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