Day 92

You have three bags that each contain two marbles.

- Bag 1 has two red marbles.
- Bag 2 has two blue marbles.
- Bag 3 has one red marble and one blue marble.

First, you choose a bag at random. Then, from that bag, you choose a marble at random and end up with a red marble. What is the probability that the other marble in the bag is also red?

If you get stuck, try diagramming the possibilities.