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)
