Question

A room has three lightbulbs. Each one has a 10% probability of burning out within the month.

What is the probability that at the end of the month at least one of the bulbs will be lit?

Answer 1

10% probability of burning out within a month

100-10 = 90% chance of not burning out within a month

90% = 0.9

(0.9)*(0.9)*(0.9) = (0.9)^3 = 0.729 = 72.9%

The probability that all 3 stay lit at the end of the month is 72.9%