Question 26·Medium·Area and Volume
The volume of a right circular cone is cubic centimeters (cm). If the radius of the base is 6 centimeters (cm), what is the height, in cm, of the cone? (The volume of a right circular cone with radius and height is given by .)
(Express the answer as an integer)
When you see a geometry volume question with a formula given, first write the formula clearly and substitute the known values immediately. Simplify step by step (square the radius, combine constants like and ) before solving for the unknown variable; this keeps arithmetic simple and reduces mistakes. Always double-check that you used the correct formula (including factors like for cones and pyramids) and that you isolated the variable in one final clean step.
Hints
Use the given formula
Start with the given volume formula for a cone, . Plug in the volume and radius you know.
Substitute the radius and volume
Replace with and with in the formula. What equation in terms of do you get?
Isolate the variable
After simplifying and , you will have a simple one-step equation in . Divide both sides by the coefficient of to solve.
Desmos Guide
Enter the cone volume expression
Type y = (1/3)*pi*36*x into Desmos, where represents the height and is the squared radius.
Set the volume and find the height
On a new line, type y = 120*pi. Click on the intersection point. The x-coordinate is the height of the cone.
Step-by-step Explanation
Write the volume formula and substitute known values
The formula for the volume of a right circular cone is
You are told the volume is and the radius is , so substitute and :
Simplify the right side of the equation
First compute :
So the equation becomes
Now simplify :
So the equation is
Solve for the height
To solve for , divide both sides of
by :
The cancels, and , so
Therefore, the height of the cone is centimeters.