SOLUTION: The mean useful life of car batteries is 57 months. They have a standard deviation of 6. Assume the useful life of batteries is normally distributed. a. Calculate the percent

Question 1194435: The mean useful life of car batteries is 57 months. They have a standard deviation of 6. Assume the useful life of batteries is normally distributed.

a. Calculate the percent of batteries with a useful life of less than 45 months. (Round your answer to the nearest hundredth percent.)
b. Calculate the percent of batteries that will last longer than 75 months. (Round your answer to the nearest hundredth percent.)
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
z=(45-57)/6=-2
probability z <-2=0.0228 or 2.28%
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this is z>3 with probability of 0.0013 or 0.13%
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