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Perimeter
Circles: word problems

Ryan used a drafting compass to draw a circle on paper. The circle was 12 cm in radius. How many square centimeters were inside the circle?

Area = π × r2

Area = π x 122 = π x 144 = 144 π cm2

π ≈ 3.14, so the area is 3.14x144=452.16 inches squared

Robert drew a circle that has a diameter of 16 inches. What is the area of his circle?

Area = π × r2

You are told that the diameter is 16 inches, so the radius is one-half of this measure, or 8 inches. Substituting the information into the area formula gives you

Area = π ×82 = π × 64 = 64π

π ≈ 3.14, so the area is 3.14x64=200.96 inches squared.

Find the circumference of the following coin (Round to the nearest whole number):

 1 Euro Coin Diameter=23.25 mm

C = π × d

Use 3.14 as an approximation for π.

C=(3.14)(23.25)≈73 mm.

Find the circumference of the following coin (Round to the nearest whole number):

 Susan B.. Anthony Dollar Radius=0.52 in

C =2πr

Use 3.14 as an approximation for π.

C=(2)(3.14)(0.52)≈3.27 in.