Circumferences and Areas of CirclesCircumferences and Areas of CirclesCOURSE 3 LESSON 8-8COURSE 3 LESSON 8-8

The diameter of a small pizza is 24 cm. Find its area. Round

to the nearest tenth.

A = r2 Use the formula for area of a circle.

= (12)2 Substitute.

The area of a small pizza is about 452.4 cm2.

Use a calculator.12 452.38934

The radius of the pizza is 24 ÷ 2, or 12 cm. Use the radius to find the area.

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Circumferences and Areas of CirclesCircumferences and Areas of Circles

Find the area of the unshaded region of the square tile with a

circle inside of it, as shown below. Round to the nearest tenth.

COURSE 3 LESSON 8-8COURSE 3 LESSON 8-8

You can separate the figure into a circle and a square.

Step 1 Find the area of the square.

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Circumferences and Areas of CirclesCircumferences and Areas of Circles

(continued)

COURSE 3 LESSON 8-8COURSE 3 LESSON 8-8

Area of square = s2

Step 2 Find the area of the circle.

Area of circle = r2

A = (12)2 Substitute 12 for s.

= 144 Simplify.

113.1 Multiply. Round to the nearest tenth.

A = (6)2 Substitute 6 for r.

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Circumferences and Areas of CirclesCircumferences and Areas of Circles

(continued)

COURSE 3 LESSON 8-8COURSE 3 LESSON 8-8

Step 3 Subtract the area of the circle from the area of the square.

The area of the shaded region is about144 cm2 – 113.1 cm2 = 30.9 cm2.

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Circumferences and Areas of CirclesCircumferences and Areas of Circles

Round to the nearest tenth.

1. Find the circumference and area of the circle.

2. Find the area.

COURSE 3 LESSON 8-8COURSE 3 LESSON 8-8

18.8 km; 28.3 km2

273.0 in.2

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