2012 PUMaC Combinatorics A3 / B5
Source:
October 5, 2019
combinatorics
Problem Statement
Jim has two fair -sided dice, one whose faces are labelled from to , and the second whose faces are labelled from to . Twice, he randomly picks one of the dice (each die equally likely) and rolls it. Given the sum of the resulting two rolls is , if is the probability he rolled the same die twice where are relatively prime positive integers, then what is ?