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McGraw Hill Integrated II, 2012

MH

McGraw Hill Integrated II, 2012 View details

4. Volumes of Prisms and Cylinders

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Exercise 58 Page 838

Recall the formula for finding the area of a circle.

7.8ft

Practice makes perfect

The area of a circle with radius r is calculated using the formula below. A=π r^2 From the exercise, we know that the area of the circle is 191ft^2. By substituting 191 for A in the formula, we can calculate r.

A=π r^2

A= 191

191=π r^2

▼

Solve for r

.LHS /π.=.RHS /π.

191/π = r^2

sqrt(LHS)=sqrt(RHS)

sqrt(191/π) = r

Rearrange equation

r = sqrt(191/π)

Use a calculator

r = 7.797255...

Round to 1 decimal place(s)

r≈ 7.8

The radius is approximately 7.8ft.

Subchapter links

Exercises p.834-838