SOLUTION: A jar contains 3 pennies, 3 nickels and 2 dimes. A child selects 2 coins at random without replacement from the jar. Let X represent the amount in cents of the selected coins. A

Question 1134960: A jar contains 3 pennies, 3 nickels and 2 dimes. A child selects 2 coins at random without replacement from the jar. Let X represent the amount in cents of the selected coins.
A) Find the probability X = 10.
B) Find the probability X = 11.
C) Find the expected value of X
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
X=10 means 2 nickels
This has probability 3/8*2/7=3/28
X=11 means a dime and a penny
This has probability 2*(3/8*2/7), which is the same as 3/8*2/7+(2/8*3/7)=12/56 or 3/14 or 6/28
The other possibilities include:
X=2 (probability is 3/28)
X=6 (probability is 2*3/8*3/7=18/56 or 9/28)
X=15 (probability is 2*3/8*2/7 or 6/28)
X=20 (probability is 2/8*1/7=1/28
The probabilities add to 1
E(X)=x*p*(X)
=6/28+54/28+90/28+20/28+30/28+66/28
=266/28
=9.5
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