Failed to connect to MySQL: Access denied for user 'examnext_online'@'localhost' (using password: YES) A box contains 4 white and 3 black balls. Another box contains 3 white and 4 black balls. A die is thrown. If it exhibits a number `<=`3, the ball is drawn from the first box. Otherwise, a ball is drawn from the second box. A ball drawn is found to be black. The probability that it has been drawn from the second box is - Sarthaks eConnect

A box contains 4 white and 3 black balls. Another box contains 3 white and 4 black balls. A die is thrown. If it exhibits a number `<=`3, the ball is drawn from the first box. Otherwise, a ball is drawn from the second box. A ball drawn is found to be black. The probability that it has been drawn from the second box is :

A box contains 4 white and 3 black balls. Another box contains 3 white and 4 black balls. A die is thrown. If it exhibits a number `<=`3, the ball is drawn from the first box. Otherwise, a ball is drawn from the second box. A ball drawn is found to be black. The probability that it has been drawn from the second box is :

A.

`3/7`

B.

`4/7`

C.

`6/17`

D.

`8/17`

Solution

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Best answer

`E_1 ->` event of drawing a ball from first box

`E_2->` Drawing a ball from `2^(nd)` box

`P(E_2/B)=(P(E_2nnnB))/(P(B))`

`=(P(E_2) P(B/E_2))/(P(E_1).P(B/E_1)+P(E_2).P(B/E_2))`

`=((1/2).(4/7))/((1/2).(3/7)+(1/2).(4/7))`

`=4/7`