Aptitude Hack#9(4-3-19)

Question:

An automobile plant contracted to buy shock absorbers from two suppliers X and Y. X supplies 60% and Y supplies 40% of the shock absorbers. All shock absorbers are subjected to a quality test. The ones that pass the quality test are considered reliable. Of X’s shock absorbers, 96% are reliable. Of Y’s shock absorbers, 72% are reliable. The probability that a randomly chosen shock absorber, which is found to be reliable, is made by Y is

A)0.288

B)0.334

C)0.667

D)0.720

ANSWER: B) 0.334

Explanation:

Probability that the absorber is reliable = 0.96*0.6 + 0.72*0.4

                                          = 0.576 + 0.288

Probability that the absorber is from y and reliable =

            (Probability that is made by Y)  X (Probability that it is reliable)

           = 0.4 * 0.72

           = 0.288

The probability that randomly picked reliable absorber is from y =

    (Probability that the absorber is from y and reliable) / (>Probability that the absorber is reliable)   = (0.288)/ (0.576 + 0.288)

   = 0.334