Question

A fair 6-sided die is rolled twice. The probability that the second roll is strictly less than the first roll can be written as a/b, where a and b are positive, coprime integers. What is the value of a+b?

Answer 1

Assume die is fair.

Rolling twice gives 36 outcomes, of which the second roll is strictly less than the first (successes) can be enumerated as follows:
21,31,32,41,42,43,51,52,53,54,61,62,63,64,65
Count how many successes there are, and divide by the size of the sample space (36).

Answer 2

thanks sir...

Answer 3

You're welcome!

It would be even better if you would not use various aliases.