To express the height as a function of the volume and the radius, we are going to use the volume formula for a cylinder: 
where
is the volume
is the radius
is the height
We know for our problem that the cylindrical can is to contain 500cm^3 when full, so the volume of our cylinder is 500cm^3. In other words:
. We also know that the radius is r cm and height is h cm, so 
and 
. Lets replace the values in our formula:
Next, we are going to use the formula for the area of a cylinder:
where
is the area
is the radius
is the height
We know from our previous calculation that, so lets replace that value in our area formula:
By the commutative property of addition, we can conclude that:
where
We know for our problem that the cylindrical can is to contain 500cm^3 when full, so the volume of our cylinder is 500cm^3. In other words:
Next, we are going to use the formula for the area of a cylinder:
where
We know from our previous calculation that
By the commutative property of addition, we can conclude that: