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9-31.
  1. The circle shown at right has a diameter of 20 cm. Homework Help ✎

    pic

    1. What measurement do you need to find in order to calculate the area inside the circle?

    2. Find the area inside the circle using the formula A = r2π. Write your answer as a product of r2 and π, and as an approximation using π = 3.14.

Recall the equation for area from the Math Notes box in this lesson.

A = r2 π

What measurement is missing in this equation?

Diameter = 2 (radius)

Solve for r.

Substitute the newly calculated radius into the area formula.

20 = 2 r

A = (10)2 π

314 cm2