A box contains 20 electric bulbs, out of which 4 are defective. Two bulbs are chosen at random from this box. The probability that at least one of these is defective is
Pick
A) 4/19	B) 7/19	C) 12/19	D) 21/95	E) None
Solution   P( None is defective)   = 16C2 / 20C2   = (16x15/2x1 ×2x1/20x19)   = 12/19.   P( at least one is defective)   = (1- 12/19)   = 7/19.   Answer 7/19
<result>B</result>
A box contains 20 electric bulbs, out of which 4 are defective. Two bulbs are chosen at random from this box. The probability that at least one of these is defective is