It is very simple problem. Just generate first 5-10 answers. Than U will see how to solve it :-)


Edited by author 27.07.2004 21:51

I don't consider this explanation for a reasonable one. If it is so easy - you are to prove it! Otherwise solving it in your way won't help to better understanding the theory behind this concrete problem.

This problem is easy. Just count number of numbers with the same digit root of its half where digit root is equal to 0,1,2,3,4,5,6,7,8,9.
Number where digit root is equal to 0 is 0.
Use /dev/brain to count the other numbers
P.S. digit root(n)=digit root(n+9)