Question

There are 121 articles in a bag. Out of which 11 are defective articles. If you just pick one article at random,
(i) what is the probability of picking the non-defective article?
(ii) If the article drawn the first time is non-defective and is not replaced, then find the probability of getting the defective article in the next draw.

Answer 1

There are 121 articles, out of which 11 are defective articles

So the number of non-defective articles is 121 -11 = 110

1. P(Non -defective article) = $\frac{110}{121}$ = $\frac{10}{11}$

2. Since the article is not replaced, the total number of articles = 121 - 1 = 120

Number of defective items = 11

$\therefore$ P( defective article) = $\frac{11}{120}$