 
Summary: Test One Mathematics 135.01 Fall 2007
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1. 5 pts. Suppose X is a random variable with variance 5. Compute Var(3X + 9).
2. 5 pts. Suppose X and Y are independent variables with expectations 3 and 4, respectively. Compute
E(XY ).
3. 10 pts. How many 12 letter strings can be made with 3 A's, 4 B's and 5 C's?
4. 10 pts. A fair six sided die is thrown 3 times. Describe a sample space for this experiment and compute
the probability that the sum of the three numbers is five.
5. 20 pts. Suppose X is a random variable such that
P(X = 1) =
1
8
, P(X = 3) =
1
2
, P(X = 5) =
3
8
