probability
posted by taylor .
A box of 6 coins (penny, nickel, dime or quarter) worth $0.67 is shaken. What is the probability that a nickel is drawn first and then a quarter? Assume no replacement and that all coins are equally likely.

Obviously there will have to be 2 pennies.
The only way I can see to get 67 cents from 6 coins is
QQDNPP
prob(nickel, quarter) = (1/6)(2/5) = 2/30 = 1/15
or
C(1,1)C(1,1)/(C6,2) = 1/15 in combination terms