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S(2*N) ≤ 2*S(N) ≤ 10*S(2*N) (Posted on 2010-01-16) Difficulty: 3 of 5
S(N) denotes the sum of the digits of a base ten positive integer N.

Prove that:

S(2*N) ≤ 2*S(N) ≤ 10*S(2*N)

No Solution Yet Submitted by K Sengupta    
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  Subject Author Date
An attempt at a proof...Dej Mar2010-01-17 13:09:21
solution (kind of)Justin2010-01-16 16:41:32
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