Question

Phil has 7 green marbles and 3 purple marbles in a bag. He removes a marble at random, records the color, puts it back, and then repeats this process until he has withdrawn 6 marbles. What is the probability that exactly three of the marbles that he removes are green? Express your answer as a decimal rounded to the nearest thousandth.

Answer 1

don't remember the formula
another approach (longer) is to do the probability tree
the P(green) = 7/10 each time because the marble was replaced