Cases:
LL -- (2/5)(1/4) = 1/10
TT -- (3/5)(2/4) = 3/10
LT -- (2/5)(3/4) = 3/10
TL -- (3/5)(2/4) = 3/10
SUM = 1/10 + 3/10 + 3/10 + 3/10
= 10/10
= 1
in combination format
choose 2 of the 5 coins = C(5,2) = 10
Two loonies = C(2,2) = 1
Two toonies = C(3,2) = 3
one of each = C(3,1)xC(2,1) = 6
total probs = 1/10 + 3/10 + 6/10 = 1
btw, "loonie" - nickname for Canadian $1 coin, it has a loon on it.
"toonie" - nickname for Canadian $2 coin
You have three toonies and two loonies in your pocket. You pull one coin out and then pull out another (without replacing the first)
1) show the total of all the probabilities is 1
2) show using combinations that part 1) is correct
1 answer
1 answer