Interesting algorithm...
Source: Taiwan 2nd TST, 2nd independent study, problem 2
August 12, 2005
algorithmpigeonhole principlenumber theoryrelatively primecombinatorics proposedcombinatorics
Problem Statement
Starting from a positive integer , we can replace the current number with a multiple of the current number or by deleting one or more zeroes from the decimal representation of the current number. Prove that for all values of , it is possible to obtain a single-digit number by applying the above algorithm a finite number of times.
There is a nice solution to this...