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 she will not buy it?

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536

19

16

736

answer is A.

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Detailed Solution

It is given a lot consists of 144 ball pens of which 20 are defective and the others are good.
The probability of an event E is given as-

P (E) = N u m b e r o f o u t c o m e s f a v o u r a b l e t o E N u m b e r o f a l l p o s s i b l e o u t c o m e s o f t h e e x p e r i m e n t

Given, total number of pens

= 144

Number of defective pens

= 20

Number of good pens

= 144 − 20

= 124

Since, Nuri will not buy a pen if it is defective.
Therefore, the probability that Nuri not buys a pen is-

∴ P (d e f e c t i v e pens) = 20144 = 536

Hence,

536

is the probability that Nuri not buys a pen.
Hence option (1) is correct.

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