Question

Two light bulbs are selected at random from a large batch of bulbs in which 5% are defective. Find the probability that:

a. Both bulbs are defective
b. At least one bulb works

Answer 1

a) 0.25% b) 99.75%

Explanation:

the chance that one bulb is defective is 0.05, so two bulbs being defective has a chance of 0.05 * 0.05 which equals 0.25%

For at least 1 bulb to work, both bulbs can't be broken. We already know that the chance for both bulbs being broke is 0.25%, so 100%-0.25% would equal the chance that at least one light bulb works, which is 99.75%