Question

A bag contains 5 marbles. There are 3 yellow marbles and 2 red marbles.

Suppose that Glen chooses a marble first and then Kris chooses one.
Answer the questions to show the probability that Kris will get a yellow marble if Glen chooses a yellow one first.

1. What is the probability that Glen will get a yellow marble? Show how you calculated this probability.
2. After Glen chooses a marble, how many are left in the bag?

3) If Glen chooses a yellow marble, how many yellow marbles are left?

4. If Glen chooses a yellow marble first, and does not put it back in the bag, what is the probability that Kris chooses a yellow marble?

Answer 1

1. Since there are 3 yellow marbles and 5 marbles in total then to find the probability we do 3/5 or 60%.

2. No matter what colour marble glen picks, he took 1 marble out of the bag so we’re left with 4 marbles.

3. We started with 3 yellow marbles, if he takes one yellow marble out of the bag then we are left with 2 yellow marbles in the bag.

4. Since there are now 4 marbles in the bag, 2 yellow marbles and 2 red marbles, the probability of choosing a yellow marble would be 2/4 or 50%.

Hope this helps