Volume of Cylinders, Cones, and Spheres
A free Geometry lesson from the “Measurement, Circles, and 3D Solids” unit, with a worked example and practice problems including step-by-step solutions.
Volume measures how much space a 3D shape encloses. A cylinder's volume equals the base area (pi * r^2) times the height. A cone with the same base and height has exactly one-third the cylinder's volume. A sphere fits the formula V = (4/3) * pi * r^3 — about two-thirds the volume of the cylinder that snugly contains it (Archimedes).
What you'll learn
- Apply V = pi * r^2 * h for a cylinder
- Apply V = (1/3) * pi * r^2 * h for a cone
- Apply V = (4/3) * pi * r^3 for a sphere
- Recognize the 1/3 cone-to-cylinder ratio and the 2/3 sphere-to-cylinder ratio
Worked example
Problem. Find the volume of a cylinder with r = 4 and h = 7 (use pi = 3.14).
- V = pi * r^2 * h = 3.14 * 16 * 7.
- = 3.14 * 112 = 351.68.
Answer: 351.68
Practice problems
1. Cylinder r = 3, h = 10 (pi = 3.14).
Show solution
- Warm-up: First identify exactly what the question is asking: Cylinder r = 3, h = 10 (pi = 3.14).
- Use inverse operations to isolate the unknown, and keep both sides balanced at every step.
- V = 3.14 * 9 * 10 = 282.6.
- Check the result by substituting or estimating: the response should match 282.6 and make sense in the original problem.
Answer: 282.6
2. Cylinder r = 5, h = 8 (pi = 3.14).
Show solution
- Warm-up: First identify exactly what the question is asking: Cylinder r = 5, h = 8 (pi = 3.14).
- Use inverse operations to isolate the unknown, and keep both sides balanced at every step.
- V = 3.14 * 25 * 8 = 628.
- Check the result by substituting or estimating: the response should match 628 and make sense in the original problem.
Answer: 628
3. Cone r = 6, h = 10 (pi = 3.14).
Show solution
- Warm-up: First identify exactly what the question is asking: Cone r = 6, h = 10 (pi = 3.14).
- Use inverse operations to isolate the unknown, and keep both sides balanced at every step.
- V = (1/3) * 3.14 * 36 * 10.
- = (1/3) * 1130.4 = 376.8.
- Check the result by substituting or estimating: the response should match 376.8 and make sense in the original problem.
Answer: 376.8
4. Cone r = 3, h = 4 (pi = 3.14).
Show solution
- Core Practice: First identify exactly what the question is asking: Cone r = 3, h = 4 (pi = 3.14).
- Use inverse operations to isolate the unknown, and keep both sides balanced at every step.
- V = (1/3) * 3.14 * 9 * 4.
- = (1/3) * 113.04 = 37.68.
- Check the result by substituting or estimating: the response should match 37.68 and make sense in the original problem.
Answer: 37.68
5. Sphere r = 6 (pi = 3.14).
Show solution
- Core Practice: First identify exactly what the question is asking: Sphere r = 6 (pi = 3.14).
- Use inverse operations to isolate the unknown, and keep both sides balanced at every step.
- V = (4/3) * 3.14 * 216.
- = 904.32.
- Check the result by substituting or estimating: the response should match 904.32 and make sense in the original problem.
Answer: 904.32
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