Question

A string of holiday lights contain 20 bulbs. the bulbs are wired in series, so that if any bulb fails, the whole string will go dark. each light has probability 0.02 of failing during the holiday season. the lights fail independently of each other. what is the probability that the string lights will remain bright?

Answer 1

This is equal to the probability that no light fail.  Probability of  one light not failing = 0.98.

P(no light fails) = 0.98^20  =   0.67  or 67%   to nearest percent.