Simplifying Calculations - 3

MULTIPLYING A NUMBER BY 11


1. Multiply a Two Digit Number by 11-- To multiply a two digit number by 11 we just write the total of both the digits between them.
e.g.               36 x 11 = 3(3+6)6 = 396

                     23 x 11 = 2(2+3)3 = 256

                     15 x 11 = 1(1+5)5 = 165

                      44 x 11 = 4(4+4)4 = 484

Now observe :

78 x 11 = 7(7+8)8 = 7(15)8 = 858 ( carry over 1 to 7 )

67 x 11 = 6(6+7)7 = 6(13)7 = 737  ( carry over 1 to 6)

59 x 11 = 5(5+9)9 = 5(14)9 = 559  ( carry over 1 to 5)

2. Multiply a Three Digit Number by 11 --  To multiply a 3- digit number by 11 we follow the steps given below.

Let us take 254 x 11 

Write 2 and 4 at the ends --------                     2 __  __   4

Add the first pair ( 2+5 ) = 7 ----                    2  7   __   4

Add the second pair ( 5+4 ) = 9--                   2  7   9     4

Therefore 254 x 11 = 2794

similarly  124 x 11 = 1364

                347 x 11 = 3 7 (11) 7 = 3817

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