Subtracting Numbers Near a Base

H.D. Motiramani

Subtracting becomes very easy if we subtract any number that is 10 or multiple of 10. The technique therefore is to add a number to both the numbers in question so that one of them becomes 10 or multiple of 10. The point becomes clear only by way of examples.

Examples:

·         46 -27

Consider 27 is close to 30 (that is 3 below 30). So add 3 to both the numbers 46 as well as 27.

          46 – 27

         +3    +3

-----------------

 =      49  -  30   = 19

 

·         84 – 39

Consider 39 is close to 40 that is 1 below 40

          84 – 39    (Add 1 to both numbers)

          +1   +1

------------------

 =       85 – 40     = 45

 

·         96 – 37

Consider 37 is close to 40 that is 3 below 40

          96 – 37

         +3    +3

------------------

=        99 – 40     = 59

 

·         88 – 58    ( Add 2 to both numbers)

+2    +2

--------------------

=       90 – 60     = 30

 

Practicing the above with more and more such examples will help in putting this technique into play for all the time to come. That will lead is to faster calculation.

 

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