There are only two ways to have 67 cents in 6 coins:
1. 1 half dollar, 3 nickels and 2 pennies
2. 2 quarters, 1 dime, 1 nickel and 2 pennies
However, since half dollars are not in circulation, there is
just one way:
2 quarters, 1 dime, 1 nickel and 2 pennies
We want
P(nickel first AND quarter second) =
P( "1 way out of 6 or
" AND "2 ways out of 5 or
) =
×
=
=
Edwin