text: find the density function for x.? a bag contains 3 dimes and 2 nickles.  two coins are selected simultaneously and at random.  let x be the random variable whose value is the value in cents of the 2 coins selected. there's 3 possibilities 1. x = 20, 2 dimes              2. x = 15, 1 dime 1 nickle 3. x = 10, 2 nickles  number of different combinations: 5c2 = 5 * 4 / 2 * 1 = 10  p(x = 20) : number of ways of picking 2 dimes out of the 3: 3c2 = 3*2*1/2*1 = 3 probability = 3/10  p(x = 15): number of ways of picking 1 coin each, 3 * 2 = 6 probability 6/10  p(x = 10) number of ways of picking 2 nickles = 1 probability 1/10  so, listed in chart form: x, p(x) 10, 1/10 15, 6/10 20, 3/10