If an integer n is to be selected at random from 1 to 900, inclusive, what is probability n(n+1) will be divisible by 9?
Choose the correct choice from the following answers:
A) 1/9 B) 1/3 C) 1/2 D) 2/9 E) 2/3
For n(n+1) to be a multiple of 9, either n or n+1 has to be a multiple of 9.   Thus n must be of the form 9k or 9k-1.   The probability is 2/9.   The answer is 2/9.
<result>D</result>
If an integer n is to be selected at random from 1 to 900, inclusive, what is probability n(n+1) will be divisible by 9?