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Summing Ones (Posted on 2013-02-27) Difficulty: 3 of 5
Find the sum
1+11+111+.......+111..111(n digits)

No Solution Yet Submitted by Danish Ahmed Khan    
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No Subject | Comment 1 of 4
an=(   10^n-1  )/9
 sn= 1/9(1+10+100+...10^n-n)
sn=1/81*(10^(1+n)-9n-1)       W r O n G

correcting my typo: 
 sn=1/81*(10^(1+n)-9n-10)      r i G h T

My original  entry was from a smartphone under very harsh conditions

Edited on February 27, 2013, 4:18 pm
  Posted by Ady TZIDON on 2013-02-27 11:15:02

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