. A bag contains 4 red and 6 black balls


A ball is drawn at random from the bag, its colour is observed and this ball along with two additional balls of the same colour are returned to the bag.

If now a ball is drawn at random from the bag, then the probability that this drawn ball is red, is

A: 15

B: 34

C: 310

D: 25

 

Best Answer

Explanation:

The probability that on drawing the first ball, the ball is black:

P(second ball red / First ball black) =4/4+8=1/3

The probability that on drawing the second ball, the ball is red:

P(second ball red / First ball red) =4+2/6+6=1/2

The probability that the second ball is red:

⇒P(First ball black) ×P(second ball red / First ball black)

+ P(second ball red) ×P(second ball red / First ball red)

⇒6/10 ×1/3+4/10×1/2

⇒2/5

Final Answer:

Hence, Option D is the correct answer.

 

 

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