Question

12 defective pens are accidentally mixed with 132 good ones. It is not possible to just look at a pen and tell whether or not it is defective. One pen is taken out at random from this lot. Determine the probability that the pen taken out is a good one.

Answer 1

total pens=132+12=144.and total good pens =132.hence, probability of pen taken out to be a good one is 132/144=66/72=33/36=11/13.

Answer 2

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Defective pens = 12

Good pens = 132

Total pens = 12 +132 = 144

Probability = 132 / 144

= 0 .91 or 11 / 13

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