This type of word problem involves the use of known formulas. Usually we used one of the formulas for either

volume or surface area, depending on what information was given, to solve for the

radius or

height of the cylinder. In one case, when the

height and

surface area are given, we were required to solve a

quadratic equation for the value of

*r*. If that

expression had not factored easily, we would have had to used the

quadratic formula.

Once values of both r and h were known, the

volume and

surface area formulas were used. These problems require careful arithmetic since it is often difficult to determine whether or not our answers are reasonable. Notice that the

surface area formula can be written in more than one way. Using more than one of these can serve as a way to check answers or make a calculation easier.