McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
5. Volumes of Pyramids and Cones
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Exercise 6 Page 844

Use the formula for the volume of a cone.

164.9cm^3

Practice makes perfect

To calculate the volume of a cone, we can use the following formula. V= 13Ï€ r^2 h Here r is the radius and h is the height of the cone. We are given that the height of the cone is 11.5cm. Let's look at the triangle including the height and the radius of the cone.

Notice that we can find r using the tangent ratio. tan 18^(∘)=r/11.5 Let's solve above equation for r.

tan18^(∘)=r/11.5
â–¼
Solve for r
11.5tan18^(∘)=r
r=11.5tan18^(∘)
r=3.73658...
r≈ 3.7

The radius of the cone's base is approximately 3.7 centimeters. Now we have all values to calculate the volume.

V=1/3Ï€ r^2 h
V=1/3Ï€ ( 3.7)^2 ( 11.5)
â–¼
Simplify right-hand side
V=1/3Ï€(13.69)(11.5)
V=164.866...
V≈ 164.9

The volume of the cone is approximately 164.9cm^3.