Find the area of a circle with a radius of 8 inches. the formula for the area of a circle is a=πr2. use 3.14 for π

What is the perimeter of a rectangular building that is 80 feet wide and 140 feet deep?

What is the value of x when x + 7 = 21?

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.