Question

Box a contains 2 black marbles and 1 white marble. box b contains 1 black marble and 1 white marble. a marble is randomly selected from box a and put into box
b. then a marble is randomly selected from box b and put into box
a. after all this, what is the expected number of black marbles in box a?

Answer 1

Box A has 2 black and 1 white
Box B has 1 black and 1 white

3(2+1) black and 1 white
 the chances of getting black marbles is 3 out 4