Question

A bag contains 7 red marbles, 8 blue marbles and 3 green marbles. If two marbles are drawn out of the bag, what is the exact probability that both marbles drawn will be red? ​

Answer 1

7/51

Explanation:

Assuming that the marbles are drawn without replacement, the probability of the first marble being drawn is 7/(7+8+3) which is 7/18.

The probability of the second marble being red is 6/17, as there are 6 red marbles left and 17 marbles in the bag.

We then multiply 7/18 and 6/17, getting 7/51.