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Big Ideas Math Geometry, 2014

BI

Big Ideas Math Geometry, 2014 View details

2. Areas of Circles and Sectors

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Exercise 7 Page 606

Recall the formula for finding the area of a circle.

About 5.32 feet

Practice makes perfect

The area of a circle with radius r is calculated using the formula below. A=π r^2 We know that the area of the circle is 89 ft^2. By substituting 89 for A in the formula, we can calculate r.

A=π r^2

A= 89

89=π r^2

.LHS /π.=.RHS /π.

89/π = r^2

Rearrange equation

r^2 = 89/π

sqrt(LHS)=sqrt(RHS)

sqrt(r^2) = sqrt(89/π)

Calculate root

r = ± 5.322553 ⋯

The radius of the circle is a measurement and therefore cannot be negative. Rounded to the nearest hundredth, the radius of the circle is approximately 5.32 feet.

Subchapter links

Communicate Your Answer p.601

Monitoring Progress p.602-605