Question

A lot consists of 144 ball pens of which 20 are defective and the others are good. Nuri will buy it and if it is a 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 1)she will buy? and
2) she will not buy it?

Answer 1

1. p(she will buy it)=favourable events/ total events
=144-20/144
=124/144
=0.96

Answer 2

Given that total number of pens n(S) = 144.

Given that total number of defective pens = 20.

That means total number of non-defective pens = 144 - 20

                                                                                 = 124.


(1) She will buy:

Let A be event that she will buy a non-defective pen

n(A) = .124.


Therefore the required probability P(A) = n(A)/n(S)

                                                                   = 124/144

                                                                   = 31/36.




(2) She will not buy it.

Let B be the event that of getting a defective pen.

n(B) = 20.

Therefore the required probability P(B) = n(B)/n(S)

                                                                  = 20/144

                                                                  = 5/36.



Hope this helps!