Question 16
12 defective pens are accidently 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.

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Solution

Total number of outcomes = 132 + 12 = 144
Number of favourable outcomes = 132
Hence, P (getting a good pen)
$= \frac{N u m b e r o f f a v o u r a b l e o u t c o m e s}{T o t a l n u m b e r o f o u t c o m e s} = \frac{132}{144} = \frac{11}{12}$

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Q. Question 21 (ii)
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Chance and Probability

Standard VII Mathematics

Question 16 12 defective pens are accidently 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.

Total number of outcomes = 132 + 12 = 144 Number of favourable outcomes = 132 Hence, P (getting a good pen) =Number of favourable outcomesTotal number of outcomes=132144=1112

Question 16
12 defective pens are accidently 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.

Total number of outcomes = 132 + 12 = 144
Number of favourable outcomes = 132
Hence, P (getting a good pen)
$= \frac{N u m b e r o f f a v o u r a b l e o u t c o m e s}{T o t a l n u m b e r o f o u t c o m e s} = \frac{132}{144} = \frac{11}{12}$