I have 5 marbles numbered 1 through 5 in a bag. Suppose I take out two different marbles at random. What is the expected value of the sum of the numbers on the marbles? Answer as a decimal to the nearest tenth.
+128406 5C 2 = 10
So we have ten possible sums
1 + 2 = 3 2 + 3 = 5 3 + 4 = 7 4 + 5 = 9
1+ 3 = 4 2 + 4 = 6 3 + 5 = 8
1 + 4 = 5 2 + 5 = 7
1 + 5 = 6
Expected value =
3 * Prob of occurence + 4 * Prob of occurence + 5*Prob of occurence + 6 * Prob of occuence +
7 * Prob of occurence + 8 * Prob of occurence + 8 * Prob of occurence
3 (1/10) + 4(1/10) + 5(2/10) + 6(2/10) + 7 (2/10) + 8 (1/10) + 9(1/10) =
3/10 + 4/10 + 10/10 + 12/10 + 14/10 + 8/10 + 9/10 =
60/10
6
