Glencoe Math: Course 3, Volume 2
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Glencoe Math: Course 3, Volume 2 View details
5. Surface Area of Cones
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Exercise 27 Page 638

The lateral area of a right cone is half the product of the circumference of the base and the slant height.

D

Practice makes perfect

We want to find the lateral area of a cone that has a diameter of 16 centimeters and a slant height of 30 centimeters. Let's draw this cone.

To find the lateral area, we must know that the lateral area of a right cone is half the product of the circumference of the base and the slant height. L.A.=1/2* 2π r* l ⇔ L.A.=π rl In this formula, r is the radius and l is the slant height of the cone. Since we know that the diameter d is equal to 16, we can divide it by 2 and get the radius of the base. r=16/2 ⇒ r= 8 With this information we are able to calculate the lateral area of the cone. To do so, we will substitute r= 8 and l= 30 into the formula for the lateral area. Let's do it!
L.A.=π rl
L.A.=π ( 8)( 30)
L.A.=π (240)
L.A.=240π
L.A.=753.982236...
L.A.≈ 753.0
The lateral area of the given cone, to the nearest tenth, is 753.0 square centimeters. This result corresponds to choice D.