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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 28 Page 629

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

About 26.4mm^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 In this case, r= 4.1. 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= 4.1

A = 1/2 π ( 4.1^2)

π ≈ 3.14

A ≈ 1/2 (3.14) (4.1^2)

Calculate power

A ≈ 1/2 (3.14) (16.81)

Write as a decimal

A ≈ 0.5 (3.14) (16.81)

Multiply

A ≈ 26.3917

Round to 1 decimal place(s)

A ≈ 26.4

We found that A ≈ 26.4, which means that the area of the semicircle is about 26.4 square millimeters.

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