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: solution by Richard)
It's all very well you doing these complicated methods, but you have to remember that average people are reading this and won't understand what you say! I'm a 17 year old Maths and Further Maths student and have never come across "mod" numers (modulo i believe)...I think that's university level! I think Eric's solution to the 13 problem and my solution to the 11 problem are the most user friendly. They may not be as elegant mathematically  but a darn more people understand what's going on!

Posted by Kirk
on 20031121 16:33:21 