Name: mike

Who is asking: Parent
Level: Middle

Question:
In a bag, there are 3 red marbles and "B" blue marbles. Two marbles are randomly selected from the bag without replacement. The probability that the two marbles are the same color is 0.5. Calculate the sum of all possible values of B. I can not figure this out can you please help.

"The probability that the two marbles are the same color is 0.5" can read as "the probability that the two marbles are of different colours is 0.5". In other words, the 3B selections of one red marble and one blue marble are exactly half of the (3+B)(2+B)/2 total possible selections. Can you work it out now?