Question

Suppose that Frida selects a ball by first picking one of two boxes at random and then selecting a ball from this box at random. The first box contains three white balls and two blue balls, and the second box contains four white balls and one blue ball. What is the probability that Frida picked a ball from the first box if she has selected a blue ball

Answer 1

Answer:

3/4

Step-by-step explanation:

Given the following :

Number of boxes = 2

First box :

White balls = 3

Blue balls = 2

Second box:

White balls = 4

Blue balls = 1

What is the probability that Frida picked a ball from the first box if she has selected a blue ball?

Probability (P) = (required outcome / Total possible outcomes)

Probability of picking first box : P(F) = 1/2

Probability of not picking second box :P(S) 1/2

Probability of picking blue from first box : P(B | F) = 3/5

Probability of picking blue, but not from first box : P(Blue not from second box) P(B|S) = 1/5

probability that Frida picked a ball from the first box if she has selected a blue ball?

P(F) * P(B|F) ÷ (P(F) * P(B|F)) + (P(S) * P(B|S))

(1/2 * 3/5) ÷ ((1/2 *3/5) + (1/2 * 1/5)

3/10 ÷ (3/10 + 1/10)

3/10 ÷ 4/10

3/10 * 10/4

= 3/4