Question

A bag contains Five blue marbles, 6 red ones and 9 green ones. Two marbles are drawn at random, one at a time, without replacing. What is the probability of selecting two blue marbles?

a 9/20
b 3/38
c 1/19
d 11/20

Answer 1

There are 20 marbles all together in the bag.
5 of them are blue.

The probability of pulling a blue one on the first draw is

5 / 20 .

After that, there are 19 marbles left in the bag, and 4 of them are blue.
The probability of pulling a blue marble on the second draw is

4 / 19 .

The probability of both draws being blue is

(5/20) x (4/19)

= 1 / 19 = 5.26...% (rounded)