Question

A box has 20 electric bulbs. Out of which 4 are defective. 2 bulbs are picked at random. Find the probablility at atleast one is defective

Answer 1

Answer:

P( None is defective)

= 16C2 / 20C2

= (16x15/2x1 ×2x1/20x19)

= 12/19.

P( at least one is defective)

= (1- 12/19)

= 7/19.