geometry
posted by tmouery on .
How many square inches are in the lateral surface area and total surface area of an aluminum can with 2 1/2 in. diameter and 4 3/4 in. height?
I've worked on this until I'm crossedeyed and it's not coming out right!

A = 2 * d ^ 2 * pi / 4 + 2 * r * pi * h
A = 2 * d ^ 2 * pi / ( 2 * 2 ) + 2 * d / 2 * pi * h
A = d ^ 2 * pi / 2 + d * pi * h
A = d * pi * ( d / 2 + h ) =
A = 2.5 * pi * ( 2.5 / 2 + 4.75 )
A = 2.5 * pi * ( 1.25 + 4.75 )
A = 2.5 * pi * 6
A = 15 * pi
A = 15 * 3.14
A = 47.1 in ^ 2