In a class of 28 students, the teacher selects four people at random to participate in a geography contest. What is the probability that this group of four students includes at least two of the top three geography students in the class? Express your answer as a common fraction.
+128475
Total number of possible sets = C(28,4) = 20, 475
Total number of sets that include 2 of the top 3 students = C(3,2) * C(25, 2) = 3*300 = 900
Total number of sets that include all three top students = C(3,3) * C(25, 1) = 1 * 25 = 25
So....the probability that we choose at least 2 of the top 3 students =
[900 + 25 ] / 20,475 = 925/ 20475 = 37 / 819
