Study Guide for final exam

Question

(Total 8) A box contains 4 quarters, 3 dimes, and 2 nickels.



a. (4) Two coins are selected at random without replacement one at a time.

Compute the probability that the first coin is a dime and the second is a nickel.

b. (4 ) Two coins are selected without replacement, what is the probability of getting exactly 2 quarters?

Answer 1

4 quarters, 3 dimes 2 nickels

randomly pick 2, what is the probability of getting a dime and then a nickel?

Pr(D 1st) = 3/(4+3+2) = 3/9 = 1/3

Pr(N 2nd) = 2/(4+2+2) = 2/8 = 1/4

Pr(D1st, N2nd) = 1/3 x 1/4 = 1/12