Eleven percent of the pens made by Apex are defective.

Only 6% of the pens made by its competitor, B-ink, are defective. Since Apex pens are cheaper than B-ink pens, an office orders 67% of its stock from Apex and 33% from B-ink. A pen is chosen at random and found to be defective. What is the probability that it was produced by Apex?

Question

Mathematics

Anahi Benton

10 September, 08:38

Eleven percent of the pens made by Apex are defective.

Only 6% of the pens made by its competitor, B-ink, are defective. Since Apex pens are cheaper than B-ink pens, an office orders 67% of its stock from Apex and 33% from B-ink. A pen is chosen at random and found to be defective. What is the probability that it was produced by Apex?

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Answers (1)

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Paloma Bowman · Answer 1

Let A be the event 'made by Apex and defective':

P (A) = 0.67 x 0.11 = 0.0737

Let B be the event 'made by B-ink and defective':

P (B) = 0.33 x 0.06 = 0.0198

Let C be the event 'made by Apex or B-ink and defective':

P (C) = P (A) + P (B) = 0.0737 + 0.0198 = 0.0935

P (defective and made by Apex) = 0.0737/0.0935 = 0.788

The answer is 0.788 or 78.8%.