The probability that a randomly selected 4​-year-old male garter snake will live to be 5 years old is 0.96679.

Question

What is the probability that at least one of nine randomly selected will not live to be 5 years​ old?

Answer 1

When doing problems like this, the method lies within the way the question is phrased. "At least one" means that anywhere between 1 and 9 garter snakes not living to 5 will fulfill the condition. Instead of adding all those probabilities, it would be better to look at what outcomes fail the condition and take the complement of that probability to get your answer.

The outcome that fails this condition is if all the snakes live to 5 years old. Since this is the case, you would do (0.96679)9 to get that probability. To then see the total probability of x>/=1 you would just do 1 - (0.96679)⁹