MathDB
Health Risk Factors Probability Problem

Source: 2014 AIME II Problem 2

March 27, 2014
probabilitynumber theoryrelatively primeAMC

Problem Statement

Arnold is studying the prevalence of three health risk factors, denoted by A, B, and C. within a population of men. For each of the three factors, the probability that a randomly selected man in the population as only this risk factor (and none of the others) is 0.1. For any two of the three factors, the probability that a randomly selected man has exactly two of these two risk factors (but not the third) is 0.14. The probability that a randomly selected man has all three risk factors, given that he has A and B is 13\tfrac{1}{3}. The probability that a man has none of the three risk factors given that he does not have risk factor A is pq\tfrac{p}{q}, where pp and qq are relatively prime positive integers. Find p+qp+q.