## Video and Examples

Finding the volume of cylinders.

 Volume of cylinders In the earlier lesson, you learned that the volume of the rectangular prism is found by multiplying the area of the base by the height of the prism. Mathematicians commonly write this as V = B • h Finding the volume of a cylinder is the exact same formula!  Step 1: Find the area of the base Step 2: Multiply it by the height In other words: Volume = (Area of base) • height Volume = (Area of a circle) • height Volume = (π • r • r) • h

 Example 1 This cylinder has a radius of 4 cm and a height of 10 cm. Find its volume. V = B • h V = (π • r • r) • h V = (3.14 • 4 • 4) • 10 V = 502.4 cm^3

 Example 2 This cylinder has a diameter of 6 cm and a height of 9 cm. What is its volume? First we need to find the radius, so we divide the diameter by 2. Radius = 6 ÷ 2 = 3 cm V = B • h V = (π • r • r) • h V = (3.14 • 3 • 3) • 9 V = 254.34 cm^3

Try this GeoGebra applet:

Move the hint slider to 0 to hide the hints and solution. Create a cylinder and then find the volume. Use the slider to check your answer.

# Self-Check

 Question 1 Find the volume of a cylinder with a radius of 7 cm and a height of 11 cm. [show answer]   V = B • h V = (π • r • r) • h V = (3.14 • 7 • 7) • 11 V = 1692.46 cm^3

 Question 2 Find the volume of a cylinder with a radius of 3 cm and a height of 8 cm. [show answer]   V = B • h V = (π • r • r) • h V = (3.14 • 3 • 3) • 8 V = 226.08 cm^3

 Question 3 Find the volume of a cylinder with a diameter of 10 cm and a height of 10 cm. [show answer]   V = B • h V = (π • r • r) • h V = (3.14 • 5 • 5) • 10 V = 785 cm^3