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The probability of getting a bad pen in a lot of 400 pens is 0.25. Find the number of good pens in the lot.

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100

200

400

300

answer is D.

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Detailed Solution

Given, probability of bad pens = 0.25. Total number of pens = 400.
The P(A) of the random experiment is,

P (A) = \frac{Number of favorable outcomes}{Total number of outcomes}

Suppose, the number of bad pens is y.
So, the number of the bad pens is,

P (E) = \frac{n (X)}{n (S)}

\Rightarrow 0.25 = \frac{y}{400}

\Rightarrow y = 100

Thus, the total number of the good pens are, 400 - 100 = 300
Therefore, the number of the good pens in the lot are 300.
Hence, option 4 is the correct answer.

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