Question

In a bag there are 4 green, 3 blue and 5 red discs.

two discs are drawn at random, and the first disc is not replaced before the second disc is drawn. Find the probability of drawing.

(a) a blue disc on the first draw.

Answer 1

3/(3+4+5)

Answer 2

isn't there three possibilities where blue can be drawn on the first draw

Answer 3

if not replaced:
4 green, 3 blue and 5 red discs= total 12
select 2 blue , there are 3 blue
(3/12)* (2/11)=6/132
= 1/22

Answer 4

the answer is 1/4 though

Answer 5

probability blue on first draw = number of blue discs / total number of discs
= 3 /12 = 1/4