Question

There are 121 articles in a bag. Out of which 11 are defective articles. If you pick only 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.

• A. (i) $\frac{11}{121}$ (ii) $\frac{12}{121}$
• B. (i) $\frac{10}{11}$ (ii) $\frac{11}{120}$
• C. (i) $\frac{12}{121}$ (ii) $\frac{10}{11}$
• D. (i) $\frac{10}{11}$ (ii) $\frac{1}{12}$

Answer 1

The correct option is B

(i) $\frac{10}{11}$ (ii) $\frac{11}{120}$

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) = $\frac{11}{120}$