How many subsets of the set {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} contain the number 5 and have 3 elements?
+130511 Since 5 is already member of the set.....we just want to choose any 2 of the remaining 9 elements for the other two members of the set.....
So
C( 9,2) = 36 subsets
+37170 10 c 3 = 120 subsets with 3 elements
each element has a 3 out of 10 chance of being in teh subset 3/10 * 120 = 36 substes with the number '5'
