Question

a factory makes lightbulbs. the probability that a bulb is defective is 1/9. if 400 lightbulbs are tested, about how many are expected to be defective

Answer 1

45.

Explanation:

so every 1/9 lightbulbs are defective, so make that L/400, (L for amount of defective bulbs).

Take the total, 400, and divide it by 9, which equals 44.4444444444. Evaluate 44.4444444444/400 and you get 0.11111111111. Evaluate 1/9, and you get 0.11111111111. So they are equivalent. But you cant have 44.4444444444 lightbulbs defective, because you can't have a lightbulb 40% defective, it either works, or doesn't work. So, round your answer up, and you get 45 total defective lightbulbs if they make 400.