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A non-trivial progression (Posted on 2015-11-17) Difficulty: 2 of 5
November 13, 2015, when expressed in MM/DD/YY format, is 11/13/15. The MM, DD and YY terms, in that order, form an arithmetic progression. It is non-trivial because the three numbers are different.

The first such date in any given century is 01/02/03. What is the last non-trivial arithmetic progression in the century?

What is the last non-trivial geometric progression in the century?

See The Solution Submitted by Steve Herman    
Rating: 4.6667 (3 votes)

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Solution d2 answers | Comment 2 of 7 |
Arithmetic: y = 2*d - m, maximized when d=31 and m=1: January 31, '61: 01/31/61.

Geometric: y = d^2 / m:

99 = 3*3*11; 33^2/11 bad, as November doesn't have 33 days.
98 = 2*7*7; 14^2/2 works: 02/14/98
            28^2/8 works better: 08/28/98


  Posted by Charlie on 2015-11-17 10:37:59
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