The breaking strength (in pounds) of a certain new synthetic is normally distributed, with a mean of 125 and a variance of 25. The material is considered defective if the breaking strength is less than 113 pounds. What is the probability that a single, randomly selected piece of material will be defective? (You may need to use the standard normal distribution table.
var=25 means std=5
113 is 12 below the mean, or 2.4 std
So, what's P(Z < -2.4)