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What is the mean number of defective pens in a box of pens?

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by BTGmoderatorLU » Mon Jul 16, 2018 1:53 pm

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Answers

A

B

C

D

E

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Difficulty—

What is the mean number of defective pens in a box of pens? The probability that there is exactly one defective pen in a box is 1 percent.

(1) The probability that all pens in the box are not defective is 96%.
(2) The probability that there is more than 1 defective pen in the box is 3%.

The OA is E.

Please, can someone assist me with this DS question? Thanks in advance!
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by GMATGuruNY » Mon Jul 16, 2018 2:05 pm
BTGmoderatorLU wrote:What is the mean number of defective pens in a box of pens? The probability that there is exactly one defective pen in a box is 1 percent.

(1) The probability that all pens in the box are not defective is 96%.
(2) The probability that there is more than 1 defective pen in the box is 3
Statements combined:
Since all the values are PERCENTS, there is no way to determine the average number of defective pens per box.
Consider the following cases:
Case 1: Each box contains 100 pens.
Case 2: Each box contains 1,000,000 pens.
Clearly, the average number of defective pens in Case 1 will be less than the average number in Case 2.
INSUFFICIENT.

The correct answer is E.
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