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Sum of Digits

Find the sum of digits of \(10^{2014} - 2014\).

Note by Dev Sharma
2 years, 2 months ago

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There'll be 2010 9's followed by 7, 9 , 8, 6. So the sum of digits becomes 18120

Vishnu C - 2 years, 2 months ago

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See there is a pattern \[10^4 - 2014 = 7986\] \[ 10^5 - 2014 = 97986 \] \[10^6 - 2014 = 997986 \] \[10^7 - 2014 = 9997986 \] Like this. \[10^n - 2014 =\underbrace{(9999\ldots)}_{(n-4)\quad times}7986 \] Thus, \[10^{2014} - 2014 = \underbrace{(9999\ldots)}_{(2010)\quad times}7986\] Thus sum of digits = \[2010 * 9 + 7 + 9 + 8 + 6 = 18120 \]

Brilliant Member - 2 years, 1 month ago

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nice observation

Dev Sharma - 2 years, 1 month ago

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thank you

Brilliant Member - 2 years, 1 month ago

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