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Glencoe Math: Course 3, Volume 2 View details

5. Surface Area of Cones

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Exercise 5 Page 634

Use the formula for the surface area of a cone.

1276.3 in.^2

Practice makes perfect

The given solid is a cone.

To calculate the surface area of a cone, we can use the known formula where r is the radius of the base and l is the slant height of the cone. S=π rl+π r^2 Looking at the diagram, we know that the diameter of the cone's base is 25 inches. By dividing by 2, we get the radius of the base. r=25/2 ⇒ r = 12.5in. We are told that the slant height of the cone equals 20 inches. By substituting r with 12.5 and l with 20 into the formula, we can calculate S.

S=π rl+π r^2

SubstituteII

r= 12.5, l= 20

S=π( 12.5)( 20)+π( 12.5)^2

▼

Evaluate right-hand side

CalcPow

Calculate power

S=π(12.5)( 20)+π(156.25)

Multiply

S=250π+156.25π

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