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 he removes a marble at random, records the color, puts it back, and then repeats this process until he has withdrawn 6 marbles.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

The probability of selecting a green marble in one turn is 7/7+3 which is 7/10. For 3 turns, we will do$\frac{7}{10} * \frac{7}{10} * \frac{7}{10} = \frac{343}{1000}$