4. Two green tiles, one red tile, and a blue tile are put into a paper bag.

Question

a) What is the probability that a green tile is drawn, followed by a blue tile, assuming the first tile is replaced before the second tile is drawn?

b) How does the answer to part a) change if the first tile drawn is not replaced?

c) Explain why these answers are different

Answer 1

P(G) = 2/4 = 1/2

P(B) = 1/4

P(G, then B) = 1/2 x 1/4 = 1/8

If the green tile is not replaced then

P(B) = 1/3 and

P(G, then B) = 1/2 x 1/3 = 1/6

Probability is the total number of ways to get a particular outcome divided by the total number of possible outcomes

If you replace the tile there is one way to get blue out of 4 possible outcomes, B/GvGvBvR = 1/4

If you don't replace then the possibilities are B/GvBvR = 1/3