Digital Sum Examples and Explanation

Digital Sum (DS)

Sum the digit of a number.

Example: 1239 = 1+2+3+9= 15 = 1+5 = 6

Where to use?

1. In complex calculations like Big Addition, Subtraction, Multiplication, Division.
2. Compound Interest Questions'

Where not to use?

1. Do not use when approximated options are given.
2. Do not use if all options have same digits.

Basic Rules

1. When DS of some digits is 9, ignore those digits whose sum is 9 and calculate the digit sum of other digits in that number.

Example: 2712 = 2+7+1+2 =12= 1+2=3

Now as per rule, ignore 2 and 7 as their sum is 9. 

Digit sum of 2712= 1+2= 3