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Big Ideas Math Geometry, 2014 View details

2. Areas of Circles and Sectors

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Exercise 8 Page 606

Write the formula to find the area of a circle and solve it for the radius.

About 11 inches

Practice makes perfect

We need to find the radius of a circle with an area of 380 in^2.

To find the radius, we will use the formula to find the area of a circle. A = π r^2 Let's substitute A=380 into the equation above and solve it for r.

A = π r^2

Substitute

A= 380

380 = π r^2

▼

Solve for r

DivEqn

.LHS /π.=.RHS /π.

380/π = r^2

SqrtEqn

sqrt(LHS)=sqrt(RHS)

sqrt(380/π) = r