Question

Suppose you have a jar with 14 red marbles and 26 black marbles. You randomly select a marble from the jar without replacement. If the marble is red, then you add 9 yellow marbles to the jar and randomly select another marble from the jar. If the first marble is black, then you add 13 blue marbles to the jar and randomly select another marble from the jar. Determine the probability of the following. (Enter each probability as a fraction.)
A)    the second marble is a blue marble

Answer 1

Alright well if you pulled out a blue marble on the second go then you can make the connection that you had originally pulled out a black marble on the first go.

so the probability of pulling out a blue marble on the second go is 13/52

"13" is the original number of blue marbles added after selecting the black marble
"52" is me simply add up all the marble in the bag..the 14 red marbles, 26 black marbles minus the 1 pulled out and not replaced so now its 25 and the 13 blue marbles added last.<span />