Probability · Question 29 · Hard
Probability question 29
A factory in Pune has two machines. Machine A makes 60% of the bolts, of which 2% are defective; machine B makes 40%, of which 3% are defective. A bolt picked at random is found to be defective. What is the probability that it was made by machine B?
- 3/5
- 3/100
- 1/2
- 2/5
Answer and explanation
Answer: C. 1/2
Explanation: P(defective from A) = 0.6 × 0.02 = 0.012 and P(defective from B) = 0.4 × 0.03 = 0.012. So P(B | defective) = 0.012 ÷ 0.024 = 1/2.
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