Unit 7 · Topic 2

Volume of Cylinders, Cones & Spheres

Overview

Apply the three key volume formulas with π.

Topic 2 of 2~56 min
Unit overview

The lesson

This lesson teaches Volume of Cylinders, Cones & Spheres. Read each section in order, work through every example on paper, then use the practice problems and quick check at the bottom.

Three formulas

When you study three formulas, slow down and write one example in your notebook without looking at the screen. That active step is what turns reading into learning.

  1. 1Cylinder: V = πr²h.
  2. 2Cone: V = (1/3)πr²h - a third of a cylinder with the same base and height.
  3. 3Sphere: V = (4/3)πr³.

Volume measures space inside a 3D object, in cubic units. Think of how many unit cubes would fill the shape.

For prisms, volume is often (area of the base) × (height). The base and height must be perpendicular for that shortcut.

Worked example

Find the volume of a cylinder with radius 3 and height 5 (use π ≈ 3.14).

  1. 1V = πr²h = 3.14 × 3² × 5.
  2. 2= 3.14 × 9 × 5 = 141.3 cubic units.

Volume measures space inside a 3D object, in cubic units. Think of how many unit cubes would fill the shape.

For prisms, volume is often (area of the base) × (height). The base and height must be perpendicular for that shortcut.

Why this matters

Volume of Cylinders, Cones & Spheres shows up constantly in apply the three key volume formulas with π. It also connects to what you will see on homework, quizzes, and the next unit in this grade.

Teachers often move fast in class. This page is here so you can pause, re-read, and practice until the idea feels familiar, not just until you have memorized a rule for one day.

Common mistakes to avoid

Rushing to the answer without writing steps. Middle-school math rewards clear work, and you catch errors earlier when steps are visible.

Mixing up similar ideas from the same topic. If two terms feel alike, make a two-column note: what is the same, what is different, and one example of each.

Key ideas from this lesson

  1. Three formulas
  2. Cylinder: V = πr²h.
  3. Cone: V = (1/3)πr²h - a third of a cylinder with the same base and height.
  4. Sphere: V = (4/3)πr³.

Video walkthrough

Khan Academy

Cylinder Volume & Surface Area

Find the volume of a cylinder using V = πr²h.

Watch on YouTube

Practice

For each problem: write your work in the box, type your answer, and check it. If you are stuck, reveal the solution one step at a time. Do not skip straight to the final answer.

Exercise 1

Try it yourself

Find the volume of a cylinder with radius 2 cm and height 10 cm. Use π ≈ 3.14.

Step-by-step solution

  1. 1V = 3.14 × 2² × 10 = 3.14 × 4 × 10.
  2. 23.14 × 40 = 125.6.
  3. 3Volume ≈ 125.6 cm³.

Exercise 2

Try it yourself

A cone has radius 3 m and height 7 m. Find its volume. Use π ≈ 3.14.

Step-by-step solution

  1. 1V = (1/3) × 3.14 × 3² × 7.
  2. 2= (1/3) × 3.14 × 9 × 7 ≈ 65.94.
  3. 3Volume ≈ 65.94 m³.

Exercise 3

Try it yourself

A sphere has radius 6 in. Find its volume. Use π ≈ 3.14.

Step-by-step solution

  1. 1r³ = 6³ = 216.
  2. 2V = (4/3) × 3.14 × 216 ≈ 904.32.
  3. 3Volume ≈ 904.32 in³.

Exercise 4

Try it yourself

A cylinder and cone share the same radius 5 and height 12. How does the cone’s volume compare to the cylinder’s?

Step-by-step solution

  1. 1Cylinder: V = πr²h.
  2. 2Cone: V = (1/3)πr²h.
  3. 3The cone’s volume is one-third the cylinder’s.

Exercise 5

Try it yourself

A cylindrical water tank has diameter 8 ft and height 15 ft. How many cubic feet of water can it hold? Use π ≈ 3.14.

Step-by-step solution

  1. 1Radius r = 4 ft.
  2. 2V = 3.14 × 4² × 15 = 3.14 × 16 × 15 = 753.6.
  3. 3Capacity ≈ 753.6 ft³.

Quick check

Answer all questions. Retake the quiz until you feel confident before moving on.

Volume of Cylinders, Cones & Spheres

Question 1 of 4

Medium

Which formula gives the volume of a sphere?

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