A box contains 5 detective and 15 non-detective bulbs. Two bulbs are chosen at random. Find the probability that both the bulbs are non-defective.

A box contains 5 detective and 15 non-detective bulbs. Two bulbs are chosen at random. Find the probability that both the bulbs are non-defective.

A 5/19

B 3/20

C 21/38

D None of these

Solution

Correct Answer: Option C

n(S) = \({}^{20}C_2\) = 190

n(E) = \({}^{15}C_2\) = 105

Therefore, P(E) = 105/190 = 21/38