Find the circumferences of the two circles. Circle A has a radius of 21 meters and Circle B has a radius of 28 meters. Use pencil and paper. Is the relationship between the radius of a circle and the distance around the circle the same for all​ circles? Explain

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.