The round base of a copper tea kettle has a diameter of 18 centimeters. What is the base's circumference?

How do you use the additive inverse to evaluate an expression that uses subtraction in a full sentence

What is the area of the triangle 10 13 12

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.