Question

From a box containing 5 blue marbles,10 red marbles,and 8 yellow marbles,Lisa removed 3 marble,one of which was blue.f she removes one more marble at random,what is the probability that it will be blur?

a. 1/4
b. 5/21
c. 1/5
d. 2/7
e. 1/6

please answer and explain

Answer 1

There were 23 marbles, of which 5 were blue
3 were removed, one of them blue

so now there are 20 marbles, of which 4 are blue

prob(blue) = 4/20 = 1/5 which is C