# Determining the equation of the volume of a cylinder

#### bwell

##### New member
Hi,

My knowledge is not too good and I'm trying to help my son find out how we would go about determining the equation of the volume of the cyclinder V(r), expressed in terms of r alone? We do not know how we would go about this without using l or h?

Any help would be really appreciative #### CaptainBlack

##### Well-known member
Hi,

My knowledge is not too good and I'm trying to help my son find out how we would go about determining the equation of the volume of the cyclinder V(r), expressed in terms of r alone? We do not know how we would go about this without using l or h?

Any help would be really appreciative Since the volume of a cylinder depends both on the radius of the base and its height, either you have misunderstood what you are being asked to do, or have not posted the complete question.

Post the question exactly as worded and any other contextual material which sets up the background for the question.

CB

#### anemone

##### MHB POTW Director
Staff member
If the cylinder is of an equilateral one, then its diameter is equal to its height, i.e. D=h. But D=2r, so we have h=2r.
Then, the volume of the equilateral cylinder, V(r)=pi(r^2)h=pi(r^2)(2r)=2pir^3.