least one die shows a 3.

5) A red bag contains 4 black and 3 white marbles. A yellow

bag contains 2 black and 5 white marbles. A fair coin is

tossed. If the coin turns up heads, a single marble is taken

from the red box. If it turns up tails, single marble is taken from

the yellow box. Find the probability that the marble taken is

black.

6) A fair coin is tossed four times. What is the probability of

having precisely two heads