A bag contains 4 red marbles and 5 blue marbles. What is the probability of randomly selecting a blue marble and then, without replacing it, selecting a red marble?

Question

anonymous · Answer

5/9 x 4/8    =     5/9 x 1/2      =      5/18

Notice how the denominator in the second factor is 8.  That's because there are only 8 marbles left at that point, of which there are still 4 red ones.

anonymous · Answer

where did you get 1/2?

anonymous · Answer

oh wait 1/2 is 4/8 simplified, right?

anonymous · Answer

yes.