Question

5 defective glasses are accidentally mixed with 20 good ones. The good ones and the defective ones look the same from the outside. If a glass is picked at random, what is the probability that the chosen glass is not defective?

• A. $\frac{3}{8}$
• B. $\frac{9}{8}$
• C. $\frac{4}{5}$
• D. $\frac{1}{5}$

Answer 1

The correct option is C

$\frac{4}{5}$

Given, Total number of glasses = 25

⇒ Total number of outcomes = 25

The Number of good ones = 20
⇒ Number of favourable outcomes = 20

Probability of an event, P(E) = $\frac{\text{number of favourable outcomes}}{\text{total number of outcomes}}$

P (getting non defective glasses) = $\frac{20}{25}=\frac{4}{5}$

$\therefore$ The probability of getting a non defective glass is $\frac{4}{5}$