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#1 Help Me ! » 9 Flips. Interesting but tough. » 2007-07-24 00:42:54

bobby_05
Replies: 13

9 Flips

abcdefghijkl
X               9
----------------
lkjihgfedcba

Suppose that N is a positive number written base 10, and that 9xN has the same digits as N but is in a reversed order. Then we shall say for short that N is a 9-Flip.

Find all 9-flips with 12 digits
Is it possible to say exactly how many 9-flips there are with precisely n digits?




I've managed to find a few by trial and error.
108910891089, 109999999989, 108900001089

But still cant reason out why.

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