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Quantitative Reasoning – Practice – Sum of digits of an expression involving exponentials!

PSA_PRACTICE_QNR43. What is the sum of the digits of (10^2014)-36?

Ans: Let us observe the pattern first:

10^2 – 36 = 64 [Zero 9s, one 6, one 4]
10^3 – 36 = 964 [One 9s, one 6, one 4]
10^4 – 36 = 9964 [Two 9s, one 6, one 4]
..
..
10^2014 – 36 = 9999….64 [Two thousand twelve 9s, one 6, one 4]

Thus, sum of all the digits= 2012*9 + 6 + 4 = 18,108 + 10 = 18,118.

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