question_answer 1)

A factory has two machines A and B. Past record shows that machine A produced 60% of the items of output and machine produced 40% of the items. Further, 2% of the item producerd by machine A and 1% produced by machine B were defective. All the items are put into one stockpile and then one item is chosen at random from this is found to be defective. What is the probability that it was produced by machine B ? 

Answer:

Let E1 and E2 are the events of selection of machines A and B respectively and       Let F = event of getting a defective item.                   Required probability = P(E2/F)