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Course 3

8-6 Volume of Pyramids and Cones

A pyramid is a three-dimensional figure whose base is apolygon, and all of the other faces are triangles.It is named for the shape of its base.

A cone has a circular base. The height of a pyramid or coneis measured from the highest point to the base along aperpendicular line.

Course 3

8-6 Volume of Pyramids and Cones

VOLUME OF PYRAMIDS AND CONES

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Course 3

8-6 Volume of Pyramids and Cones

Additional Example 1A: Finding the Volume of

Pyramids and Cones

Find the volume of the figure. Use 3.14 for !.

13

V = • 14 • 6

V = 28 cm3

V = Bh1

3

B = (4 • 7) = 14 cm212

Slant height-the height of one of

the sides. It’soutside the pyramid.

Course 3

8-6 Volume of Pyramids and Cones

Additional Example 1B: Finding the Volume of

Pyramids and Cones

13

V = • 9! • 10

V = 30! " 94.2 in3

V = Bh1

3

B = !(32) = 9! in2

Use 3.14 for !.

Find the volume of the figure. Use 3.14 for !.

Area of the base

Course 3

8-6 Volume of Pyramids and Cones

13

V = • 17.5 • 7

V " 40.8 in3

V = Bh1

3

B = (5 • 7) = 17.5 in212

5 in.

7 in.

7 in.

Find the volume of the figure. Use 3.14 for !.

Area of 1 face

Course 3

8-6 Volume of Pyramids and Cones

13

V = • 9! • 7

V = 21! " 65.9 m3

V = Bh1

3

B = !(32) = 9! m2

Use 3.14 for !.

Check It Out: Example 1B

7 m

3 m

Find the volume of the figure. Use 3.14 for !.

Course 3

8-6 Volume of Pyramids and Cones

Exploring the Effects of Changing Dimensions

A cone has a radius of 3 ft. and a height of 4 ft.Explain whether tripling the height would have thesame effect on the volume of the cone as tripling theradius.

*When the height of the cone is tripled, the volume istripled.*When the radius is tripled, the volume becomes 9 timesthe original volume.