Question : A purse contains 2 six-sided dice One is a normal fair die, while the other has two 1’s , and two 5’s 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 a 25% chance of picking a fair die. The die is rolled and shows up the face 3. The probability that a fair die was picked up is
(A) 1/7
(B) 1/4
(C) 1/6
(D) 1/24
Answer : option (A)
Solution :

