If the outer diameter of a metal pipe is 2.84 inches and the inner diameter is 1.94 inches the thickness of the metal is?

The answer is the difference between the radii of the inner circumscribed circle and the outer circumscribed circle. The radii equal half of the corresponding diameters; therefore, the thickness is 1/2(2.84 - 1.94) = 0.450 inches, where the last digit is depressed because it may not be accurate within + 1. (The difference between 2.84 and 1.94 has only two significant digits.)