Class 10

Math

All topics

Probability I

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 ?

Number of defective pens, $=20$

So, number of good pens, $=144−20=124$

Now, Nuri will buy a pen if it is good.

(i)So, probability Nuri will buy a pen = $144124 =3631 $

(ii) Probability of Nuri not buying a pen $=14420 =365 $