A number of 50 digits has all its digits equal to 1 except the 26th digit. If the number is divisible by 13, then find the digit in the 26th place.
(In reply to re(5): solution
With all due respect, I must agree with Kirk. And, half the reason (IMHO) of posting to flooble is to explain (in a USEFUL way) one's thought processs to others who might read it.
Some of your earlier comments make little sense to me... (particularly this one) and I am familiar with modular arithmetic.
I (and many other common submitters), generally, endeavor to write solutions/comments that include much detail--perhaps more detail than some require, but enough to help those, who are not so familiar with the subject matter, to understand the related thought processes and relationships and perhaps understand the issue better.
When one submits a solution, it should be more than an answer. It should be, if at all possible, a straightforward method/algorithm of how to come by the answer. Failing that, one might provide hyperlinks that readers could follow to learn more about the solution or subject matter.
Edited on November 23, 2003, 2:12 am