Question

A container of oatmeal in the shape of a cylinder has a surface area of 47.5pi square centimeters. The height of the container is 7 centimeters. What is the radius of the base of the cylinder?

Answer 1

2.5 cm

Explanation:

The total surface area of a cylinder is the sum of the two base areas and the lateral area.

S = 2πr² +2πrh

Filling in the given information, we have ...

47.5π = 2πr² +14πr

23.75 = r² +7r . . . . . divide by 2π

23.75 +12.25 = r² +7r +12.25 . . . . . . add the square of 7/2 to complete the square

36 = (r +3.5)² . . . . simplify a bit

6 = r +3.5 . . . . . . . take the positive square root

2.5 = r . . . . . . . . . . subtract 3.5

The radius of the base of the cylinder is 2.5 cm.