Question

An opaque bag contains 5 green marbles, 3 blue marbles and 2 red marbles. If two marbles are drawn at random WITHOUT replacement, what is the probability of drawing a blue marble given the first marble was red?

Answer 1

1/9 is the probability

Answer 2

Answer:  $\dfrac{1}{3}$

Step-by-step explanation:

Given : An opaque bag contains 5 green marbles, 3 blue marbles and 2 red marbles.

Total marbles = 5+3+2=10

Now, if it given that the a red marble is already drawn, then the total marbles left in the bag = 10-1=9

But the number of blue marbles remains the same.

Now, the probability of drawing a blue marble given the first marble was red :-

$=\dfrac{\text{Number of blue marbles}}{\text{Total marbles left}}\\\\=\dfrac{3}{9}=\dfrac{1}{3}$

Hence, the required probability = $\dfrac{1}{3}$