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2 ways to prove it (Posted on 2017-10-31) Difficulty: 2 of 5
For every positive integer n: 10n+18*n-1 is divisible by 27.

The above statement can be proven by more than one way.

Find at least 2 distinct methods.

No Solution Yet Submitted by Ady TZIDON    
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Solution Method 1 | Comment 1 of 2
(10n+18*n-1)/9 (mod 3) = ((10n-1)/9 (mod 3) + (18*n)/9 (mod 3) = n (mod 3) + 2*n (mod 3) = 3*n (mod 3) = 0
  Posted by chun on 2017-10-31 12:29:13
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