How do you check if a number is divisible by 11?

[irony of truth]

Hello

I would like to know how to determine whether a number is divisible by 11 or not... say 209.

I know the divisibility rules from 2 to 10... but how about 11?

 

[CrankFan]

see here

http://mathforum.org/dr.math/faq/faq.divisibility.html

 

[HallsofIvy]

Add and subtract the digits alternately. The result is divisible by 11, if and only if the original number is.