Question

a box contains 12 electric lamps of which 5 are defective. A man selects three lamps at random. what is the expected number of defective lamps in his selection

Answer 1

probability
number of favourable outcome/ number of total outcome
=5/12

hence the probability of getting defective lamps in his selection is 5/12.

Answer 2

Answer:

Let x denote the number of defective lamps, x can assume the values 0, 1, 2, 3.