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Question
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?
Solution
Total number of pens = 144
Total number of defective pens = 20
Total number of good pens = 144 − 20 = 124
P (she will not buy a pen) = `1 - 31/36 `
`= (36 - 31)/36 `
`= 5/36`
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