SOLUTION: A bag contains 6 red marbles, 5 blue marbles and 7 green marbles. If three marbles are drawn out of the bag, what is the exact probability that all three marbles drawn will be gree

At the start, there are  6 + 5 + 7 = 18  marbles in the bag.

Of them, 7 marbles are green.


The probability that the first drawn marble is green equals  .

After that, we have 17 marbles in the bag with 6 green marbles.
So, the probability that the first two drawn marbles are green equals  .


Analyzing further in the same way, we find that the probability
that the first three drawn marbles are green equals 

     = reduce the fractions =  = .   ANSWER