Math 1431 – Spring 2003 – Test #2 – Practice
Question 3 Answer

The sample space is:

1 + 1 = 21 + 2 = 31 + 3 = 41 + 4 = 51 + 5 = 61 + 6 = 7
2 + 1 = 32 + 2 = 42 + 3 = 52 + 4 = 62 + 5 = 72 + 6 = 8
3 + 1 = 43 + 2 = 53 + 3 = 63 + 4 = 73 + 5 = 83 + 6 = 9
4 + 1 = 54 + 2 = 64 + 3 = 74 + 4 = 84 + 5 = 94 + 6 = 10
5 + 1 = 65 + 2 = 75 + 3 = 85 + 4 = 95 + 5 = 105 + 6 = 11
6 + 1 = 76 + 2 = 86 + 3 = 96 + 4 = 106 + 5 = 116 + 6 = 12

(a). P(X<2) = 0
(b). P(X≥7) = 21/36 = 7/12
(c). P(X≤11) = 1 – P(X>11) = 1 – 1/36 = 35/36
(d). P(X<11) = 1 – P(X≥11) = 1 – 3/36 = 33/36 = 11/12
(e). P(X=5) = 4/36 = 1/9
(f). P(X=5 or X>10) = 1/9 + 3/36 = 7/36