Question

Pierre asks Sherry a question involving the theoretical probability of a compound event in which you flip a coin and draw a marble from a bag of marble. The bag of marbles contains 3 white marbles, 8 green marbles, and 9 black marbles. Sherry’s answer, which is correct, is __ 12/40. What was Pierre’s question?

Answer 1

Pierre's question : What is the probablity of flipping a head and picking a white or black marble at the same time?

The probability of flipping a head is 50%, or 1/2
The probably of randomly picking a white or black marble is (3+9)/(3+9+8) = 12/20.

So, the probability of they happening simultaneously is 1/2 x 12/20 = 12/40.