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The penultimate digit (Posted on 2018-11-12) Difficulty: 2 of 5
A problem from the 1996 Georg Mohr mathematics competition in Denmark:

n is a positive integer. The next-to-last digit in the decimal expression
of n^2 is 7.
What’s the last digit?

Please provide your reasoning, not only the digit.

No Solution Yet Submitted by Ady TZIDON    
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Comments: ( You must be logged in to post comments.)
  Subject Author Date
solnSteven Lord2018-11-12 17:46:50
SolutionsolutionPaul2018-11-12 11:36:43
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