# ACT Math : How to find the surface area of a cylinder

## Example Questions

### Example Question #11 : Cylinders

What is the surface area of a cylinder with a radius of 2 cm and a height of 10 cm?

48π cm2

40π cm2

32π cm2

56π cm2

36π cm2

48π cm2

Explanation:

SAcylinder = 2πrh + 2πr2 = 2π(2)(10) + 2π(2)2 = 40π + 8π = 48π cm2

### Example Question #1 : How To Find The Volume Of A Cylinder

If a cylinder has a radius, , of 2 inches and a height, , of 5 inches, what is the total surface area of the cylinder?

Explanation:

The total surface area will be equal to the area of the two bases added to the area of the outer surface of the cylinder. If "unwrapped" the area of the outer surface is simply a rectangle with the height of the cylinder and a base equal to the circumference of the cylinder base. We can use these relationships to find a formula for the total area of the cylinder.

Use the given radius and height to solve for the final area.

### Example Question #121 : Solid Geometry

What is the surface area of a cylinder with a base diameter of  and a height of ?

Explanation:

Area of a circle

Circumference of a circle

Surface area of a cylinder

### Example Question #1 : How To Find The Surface Area Of A Cylinder

What is the surface area of a cylinder with a radius of  and a height of ? Give your answer in terms of .

Explanation:

To find the surface area of a cylinder with radius  and height  use the equation:

Thus for a cylinder with a radius of 5 and a height of 7 we get:

### Example Question #11 : Cylinders

Find the surface area of a cylinder whose height is 6 and radius is 7.

Explanation:

To solve, simply use the formula for surface area of a cylinder.

First, identify all known information.

Height = 6

Substitute these values into the surface area equation and solve.

Thus,

### Example Question #1 : How To Find The Surface Area Of A Cylinder

A grain silo in the shape of a right circular cylinder is erected vertically, as shown below. The silo is then covered with corrugated steel. If the cylinder is  tall and has a circumference of , how much corrugated steel, in square meters, must be used to cover the visible portion of the silo?

Explanation:

The surface area of a cylinder can be calculated using the following formula:

In this equation, the variable, , is the radius of the base of the cylinder and  is the height of the cylinder.

In this case, we must also remember not to include one of the two  measurements, since the bottom face that is in contact with the ground will not be covered with corrugated steel. We need to modify our surface area formula in the following way:

We are given the circumference of the cylinder; therefore, we can use this information to solve for the radius.

Since the circumference is , we know the radius is 3. Now we can insert these values to the modified surface area equation and solve for the coverable surface area of the silo.

### Example Question #1 : How To Find The Surface Area Of A Cylinder

The volume of a cylinder is . If the radius of the cylinder is , what is the surface area of the cylinder?