Question

Assume that the box contains 10 balls:
4 red, 4 blue, and 2 yellow. As in the text, you draw one ball, note its color, and if it is yellow replace it. If it is not yellow you do not replace it. You then draw a second ball and note its color.

What is the probability that the second ball drawn is red?

Answer 1

4 out of 10. The problem says you replace the ball if it is not yellow. The first time you picked up a ball, you replaced it because it says you drew a second ball. Therefore, the probability is the number of red balls over the number of all of the balls.