There is 3 green en 2 red balls in a bag. Two balls are taken out of the bag after each other and placed back into the bag. What is the probability that both the balls that are drawn will be green?

Question

Probability

Answer 1

There are 5 balls in the bag so the probability of drawing a green ball first is ⅗. If the ball is not placed back in the bag immediately, there will be 4 balls left in the bag, 2 of which are green. If the second ball is now drawn, the probability of drawing a green is 2/4=½. Therefore the probability of drawing two green balls is ⅗×½=3/10 or 0.3 or 30%.

If the first ball drawn had been placed back in the bag before the second ball had been drawn the probability would have been ⅗²=9/25=0.36 or 36%.