A purse contains 2 six sided dice. One is a normal fair die, while the other has 2 ones, 2 threes and 2 fives. A die is picked up and rolled. Because of some secret magnetic attraction of the unfair die, there is 75% chance of picking the unfair die and 25% chance of picking a fair fie. The die is rolled
and shown up the face 3. The probability that a fair die was picked up, is

see full answer

21% of IItians & 23% of AIIMS delhi doctors are from Sri Chaitanya institute !!

An Intiative by Sri Chaitanya

1/4

1/6

1/7

1/24

answer is A.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

P(N)=P(Normal die)= $\frac{25}{100} = \frac{1}{4}$

P(B)=P(baised die)= $\frac{75}{100} = \frac{3}{4}$

E= getting 3

P(E/N)=1/6,P(E/B)=2/6=1/3

$P (N / E) = \frac{P (N) P (E / N)}{P (N) P (E / N) + P (B) P (E / B)}$

Using Baye’s theorem, $P (N / E) = \frac{\frac{1}{4} \cdot \frac{1}{6}}{\frac{1}{4} \cdot \frac{1}{6} + \frac{3}{4} \cdot \frac{1}{3}} = \frac{1}{7}$

Watch 3-min video & get full concept clarity