Question

A lot consists of 144 ball pens of which 20 are defective arid 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?

Answer 1

Total number of pens, n(S) = 144. 

Number of defective pens = 20 

∴ Number of good pens = 144 – 20 = 124 

(i) Number of good pens Nun buys = 124 

∴ n(E) = 124

(ii) Number of pens which Nuri do not buy = 20 

∴ n(E) = 20