A lot consists of 144 ball pens of which 20 are defective and the others are good. Nuri will buy a pen if it is good, but will not buy if it is defective. The shopkeeper draws one pen at random and gives it to her. What is the probability that
(i) She will buy it ?
(ii) She will not buy it ?
📚 Submitted Answer
Solution:
The total number of pens in the lot is 144.
Out of these, 20 pens are defective, and the remaining 144 – 20 = 124 pens are good.
(i) Probability that she will buy the pen (i.e., it is good):
Nuri buys the pen only if it is good.
So, the number of good pens = 124.
Total number of pens = 144.
The probability that Nuri will buy the pen (it is good) is:
P(Good pen) = Number of good pens /Total number of pens = 124/144
Simplifying the fraction:
P(Good pen) = 31/36
(ii) Probability that she will not buy the pen (i.e., it is defective):
Nuri will not buy the pen if it is defective.
So, the number of defective pens = 20.
The probability that Nuri will not buy the pen (it is defective) is:
P(Defective pen) = Number of defective pens / Total number of pens = 20/144
Simplifying the fraction:
P(Defective pen) = 5/36
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