What is the surface area of a cylinder with a radius of 4 and a height 6?

Answer 1

The surface has three parts: two circles and a "tube". The area of a circle is pi times the square of the radius, so the area of each of the two circles is pi times 16 square units. If you remember that the area of a rectangle is its width times its height, you can remember the surface area of a tube by remembering that a rectangle can be easily converted to a tube just by curving the width until the sides touch. Then what was width times height becomes circumference times height. Since circumference is not given, it has to be calculated from the radius. The circumference of a circle is equal to pi times its diameter, or pi times two times its radius, so the surface area of the tube is pi times 48 square units. The last step is adding the three areas together.