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Home > MC2 > Chapter 5 > Lesson 5.3.4 > Problem 5-125

5-125.
  1. The circle shown below has a diameter of 20 cm. Homework Help ✎

    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 = r2 π. 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 of Lesson 5.3.4.

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