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A round coin has a diameter of 3 centimeters. What is the circumference of the coin?

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A barbecue grill is a circle with a diameter of 2.2 feet. What is the circumference of the grill?

6.908 ft

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The top of a pie tin is a circle with a diameter of 9.5 inches. What is the circumference of the top?

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A circle has a circumference of 163.28 inches. Find the diameter.

52 in.

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A circle has a circumference of 59.66 feet. Find the diameter.

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A circle has a circumference of 17.27 meters. Find the diameter.

5.5 m

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A circle has a circumference of 80.07 centimeters. Find the diameter.

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In the following exercises, find the radius of the circle with given circumference.

A circle has a circumference of 150.72 feet.

24 ft

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A circle has a circumference of 251.2 centimeters.

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A circle has a circumference of 40.82 miles.

6.5 mi

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A circle has a circumference of 78.5 inches.

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Find the Area of Irregular Figures

In the following exercises, find the area of the irregular figure. Round your answers to the nearest hundredth.

In the following exercises, solve.

A city park covers one block plus parts of four more blocks, as shown. The block is a square with sides 250 feet long, and the triangles are isosceles right triangles. Find the area of the park.

A square is shown with four triangles coming off each side.

187,500 sq. ft

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A gift box will be made from a rectangular piece of cardboard measuring 12 inches by 20 inches, with squares cut out of the corners of the sides, as shown. The sides of the squares are 3 inches. Find the area of the cardboard after the corners are cut out.

A rectangle is shown. Each corner has a gray shaded square. There are dotted lines drawn across the side of each square attached to the next square.
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Perry needs to put in a new lawn. His lot is a rectangle with a length of 120 feet and a width of 100 feet. The house is rectangular and measures 50 feet by 40 feet. His driveway is rectangular and measures 20 feet by 30 feet, as shown. Find the area of Perry’s lawn.

A rectangular lot is shown. In it is a home shaped like a rectangle attached to a rectangular driveway.

9400 sq. ft

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Denise is planning to put a deck in her back yard. The deck will be a 20-ft by 12-ft rectangle with a semicircle of diameter 6 feet, as shown below. Find the area of the deck.

A picture of a deck is shown. It is shaped like a rectangle with a semi-circle attached to the top on the left side.
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Everyday math

Area of a Tabletop Yuki bought a drop-leaf kitchen table. The rectangular part of the table is a 1-ft by 3-ft rectangle with a semicircle at each end, as shown. Find the area of the table with one leaf up. Find the area of the table with both leaves up.

An image of a table is shown. There is a rectangular portion attached to a semi-circular portion. There is another semi-circular leaf folded down on the other side of the rectangle.

  1. 6.5325 sq. ft
  2. 10.065 sq. ft

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Painting Leora wants to paint the nursery in her house. The nursery is an 8-ft by 10-ft rectangle, and the ceiling is 8 feet tall. There is a 3-ft by 6.5-ft door on one wall, a 3-ft by 6.5-ft closet door on another wall, and one 4-ft by 3.5-ft window on the third wall. The fourth wall has no doors or windows. If she will only paint the four walls, and not the ceiling or doors, how many square feet will she need to paint?

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Writing exercises

Describe two different ways to find the area of this figure, and then show your work to make sure both ways give the same area.

A geometric shape is shown. It is a vertical rectangle attached to a horizontal rectangle. The width of the vertical rectangle is 3, the left side is labeled 6, the bottom is labeled 9, and the width of the horizontal rectangle is labeled 3. The top of the horizontal rectangle is labeled 6, and the distance from the top of that rectangle to the top of the other rectangle is labeled 3.

Answers will vary.

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A circle has a diameter of 14 feet. Find the area of the circle using 3.14 for π using 22 7 for π . Which calculation to do prefer? Why?

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Self check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

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After looking at the checklist, do you think you are well prepared for the next section? Why or why not?

Practice Key Terms 1

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Source:  OpenStax, Prealgebra. OpenStax CNX. Jul 15, 2016 Download for free at http://legacy.cnx.org/content/col11756/1.9
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