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Glencoe Math: Course 3, Volume 2

GM

Glencoe Math: Course 3, Volume 2 View details

5. Surface Area of Cones

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Exercise 1 Page 634

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

678.6ft^2

Practice makes perfect

We want to find the lateral area of the given cone.

To do so, 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. With this information we are able to calculate the lateral area of the cone. To do so, we will substitute r= 12 and l= 18 into the formula for the lateral area. Let's do it!

L.A.=π rl

r= 12, l= 18

L.A.=π ( 12)( 18)

Multiply

L.A.=π (216)

CommutativePropMult

Commutative Property of Multiplication

L.A.=216π

Use a calculator

L.A.=678.584013...

Round to 1 decimal place(s)

L.A.≈ 678.6

The lateral area of the given cone, to the nearest tenth, is 678.6 square feet.

Subchapter links

Guided Practice p.634

Independent Practice p.635-636

H.O.T. Problems p.636

Extra Practice p.637

Standardized Test Practice p.638

Common Core Review p.638