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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