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(sod(x))^2 = x+2 (Posted on 2011-01-26) Difficulty: 3 of 5
Determine the probability that for a base ten positive integer x chosen at random from 1 to 9999 inclusively, this relationship is satisfied: (sod(x))2 = x+2, where sod(n) denotes the sum of the digits in the base ten representation of n.

No Solution Yet Submitted by K Sengupta    
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Solution Solution (Using Excel) | Comment 1 of 3
There are 7 possible integers within that range:

2, 23, 62, 119, 194, 287, 398


Probability = 7/9999 ≈0.0007000700070 . . .
  Posted by hoodat on 2011-01-26 14:38:40
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