10.1.2 Surface Area of Pyramids and Cones (continued)
Example 5 Problem-Solving Application
The diameter of the base of a right cone made by folding a two-dimensional shape is determined in this example. The circumference of the base of the cone is equal to three quarters of the length of the circumference of the two-dimensional circle. The circumference of the two-dimensional circle is 2 π ⋅ 8 = 16 π . Three quarters of this value is 12 π . This is the circumference of the base of the cone, or 2 πr . Set these two values equal to each other and solve for r . The radius of the cone is 6 inches. The diameter of the cone is 12 inches.
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