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Glencoe Math: Course 2, Volume 2

GM

Glencoe Math: Course 2, Volume 2 View details

2. Area of Circles

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Exercise 11 Page 627

The area of a semicircle equals half the product of π and the square of its radius.

About 163.3yd^2

Practice makes perfect

Let's consider the given semicircle.

Circle

We want to find the area of the semicircle. Recall that the area A of a semicircle equals half the product of π and the square of its radius r. A = 1/2 π r^2 Since the diameter of the semicircle is 20.4 inches, the radius of the semicircle is ( 12* 20.4) yards or 10.2 yards. Let's calculate the area using this information. Remember, we are asked to use 3.14 as an estimation of π.

A = 1/2 π r^2

r= 10.2

A = 1/2 π ( 10.2^2)

π ≈ 3.14

A ≈ 1/2 (3.14) (10.2^2)

Calculate power

A ≈ 1/2 (3.14) (104.04)

Write as a decimal

A ≈ 0.5 (3.14) (104.04)

Multiply

A ≈ 163.3428

Round to 1 decimal place(s)

A ≈ 163.3

We found that A ≈ 163.3, which means that the area of the semicircle is about 163.3 square yards.

Subchapter links

Guided Practice p.626

Independent Practice p.627-628

H.O.T. Problems p.628

Standardized Test Practice p.628-630

Extra Practice p.629

Common Core Review p.630