# 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?

QuestionsCategory: Managerial StatisticsA 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?
MyIQ Staff Staff asked 4 years ago
Anonymous answered 4 years ago

Please remember that Maximum portability is 1.

So we can get total probability of non defective bulbs and subtract it form 1 to get total probability of defective bulbs.

So here we go,
Total cases of non defective bulbs: 16 C 2 = 120
Total cases= 20 C  2= 190
Probability= 120/ 190
Probability of at least one defective= 1- (12/19)= 7/19