Question 11·Medium·Area and Volume
A right circular cylinder has a height of centimeters and a base diameter of centimeters. What is the volume, in cubic centimeters, of the cylinder?
For cylinder volume questions on the SAT, start by recalling the formula and immediately check whether the problem gives a radius or a diameter—if it gives a diameter, divide by 2 to get the radius. Keep as a symbol instead of approximating it, substitute the radius and height carefully, make sure you square only the radius, and then match your simplified expression to the closest answer choice written in terms of . This avoids unnecessary calculation and reduces rounding errors.
Hints
Identify the needed formula
Think about the standard formula for the volume of a right circular cylinder in terms of its radius and height.
Be careful with diameter vs. radius
The problem gives the diameter of the base. How do you find the radius from the diameter?
Substitute correctly into the formula
Once you have the radius and the height, plug them into and simplify carefully. Pay attention to squaring the radius and to the order of multiplication.
Desmos Guide
Confirm the radius
In a Desmos expression line, type 8/2 to verify that the radius is 4 centimeters.
Compute the cylinder volume
In a new expression line, type pi*(4^2)*9. Desmos will show a decimal approximation and may also display an exact expression of the form (number)*pi; the number multiplying pi is the volume in cubic centimeters that matches one of the answer choices.
Step-by-step Explanation
Recall the cylinder volume formula
For a right circular cylinder, the volume formula is , where is the radius of the circular base and is the height of the cylinder. We are given the height cm and the base diameter, not the radius.
Find the radius from the diameter
The diameter of the base is 8 cm. The radius is half the diameter, so cm. Now we have and to use in the formula.
Substitute and compute the volume
Substitute and into : . Therefore, the volume is cubic centimeters, which corresponds to choice B.