Today we will learn a property of digital root to check addition sums.
REMEMBER
The digital root of a sum is the sum of the digital roots of the numbers being added.
Above statement may look confusing, but it will be easy in a short while. Lets understand this by a example.
1. Add two numbers 354 + 212.
2. Digital root of 354 is 3
3. Digital root of 212 is 5
4. Now add 3+5 is 8.
This implies that Digital root of 354+212 will also be 8. Let's verify.
5. Addition of 354+212=566
6. Digital root of 566 is 5+6+6=17 again 1+7 = 8
Hence the digital root of the final answer is equal to the sum of the digital roots of 2 numbers.
Using this property multiple choice questions can be solved in seconds. For example.
Example 1. 2827+3285+5025 = ?
(a) 10137 (b) 11137 (c) 10187 (d) 11257
Now to solve this problem find digital root of nos:
DR of 2827 is 1
DR of 3285 is 9
DR of 5025 is 3
Add 9+1+3=13 again 1+3=4
Now find the digital root of all the answer, the digital root of which ever option matches with 4 will be the answer. Let's see.
(a) 10137-- Digital root is 3
(b) 11137---Digital root is 4
(c) 10187---- Digital root is 8
(d) 11257--- Digital root is 7
So the answer is option (b).
This way, by adding digital roots we can get the correct answer in competitive exams and it saves lot of time.
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