Area: Circles
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Area: Circles PRE-ALGEBRA LESSON 10-3 (For help, go to Lesson 4-7.) Simplify each expression. 1. 3.14 • 4 2 2. 3.14 • 5 2 3. 3.14 • 9 2 4. 3.14 • 0.5 2 Check Skills You’ll Need 10-3
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Area: Circles. PRE-ALGEBRA LESSON 10-3. (For help, go to Lesson 4-7.). Simplify each expression. 1. 3.14 • 4 2 2. 3.14 • 5 2 3. 3.14 • 9 2 4. 3.14 • 0.5 2. Check Skills You’ll Need. 10-3. Area: Circles. PRE-ALGEBRA LESSON 10-3. Solutions 1. 3.14 • 4 2 2. 3.14 • 5 2 - PowerPoint PPT Presentation
Transcript of Area: Circles
Area: CirclesArea: CirclesPRE-ALGEBRA LESSON 10-3PRE-ALGEBRA LESSON 10-3
(For help, go to Lesson 4-7.)
Simplify each expression.
1. 3.14 • 42 2. 3.14 • 52
3. 3.14 • 92 4. 3.14 • 0.52
Check Skills You’ll Need
10-3
Area: CirclesArea: CirclesPRE-ALGEBRA LESSON 10-3PRE-ALGEBRA LESSON 10-3
Solutions
1. 3.14 • 42 2. 3.14 • 52
= 3.14 • 4 • 4 = 3.14 • 5 • 5= 50.24 = 78.5
3. 3.14 • 92 4. 3.14 • 0.52
= 3.14 • 9 • 9 = 3.14 • 0.5 • 0.5= 254.34 = 0.785
10-3
Area: CirclesArea: Circles
Find the exact area of a circle with diameter 20 in.
PRE-ALGEBRA LESSON 10-3PRE-ALGEBRA LESSON 10-3
A = r 2
= (10)2 r = d; r = 1012
= 100 Simplify.
The area is 100 in.2.
Quick Check
10-3
Area: CirclesArea: Circles
A TV station’s weather radar can detect precipitation in a circular region having a diameter of 100 mi. Find the area of the region.
PRE-ALGEBRA LESSON 10-3PRE-ALGEBRA LESSON 10-3
A = r 2
The area of the region is about 7,850 mi2.
= (50)2 r = d; r = 5012
= 2,500 exact area
(2,500)(3.14) Use 3.14 for .
= 7,850 approximate area
Quick Check
10-3
Area: CirclesArea: Circles
A pound of grass seed covers approximately 675 ft2. Find the
area of the lawn below. Then find the number of bags of grass seed
you need to buy to cover the lawn. Grass seed comes in 3-lb bags.
PRE-ALGEBRA LESSON 10-3PRE-ALGEBRA LESSON 10-3
Area of region that is one fourth of a circle:
area of circle = r 2
area of quarter circle = r 2
A (3.14)(15)2 Replace with 3.14 and r with 15.
= 176.625 ft2
14
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10-3
Area: CirclesArea: Circles
(continued)
PRE-ALGEBRA LESSON 10-3PRE-ALGEBRA LESSON 10-3
Area of region that is a rectangle:
area of rectangle = bh
A = 45 • 25 Replace b with 45 and h with 25.
= 1,125 ft2
The area of the lawn is about 177 ft2 + 1,125 ft2 = 1,302 ft2.
You need to buy one 3-lb bag of grass seed.
1,302 ÷ 675 1.93 Divide to find the number of pounds of seed.
Quick Check
10-3
Area: CirclesArea: CirclesPRE-ALGEBRA LESSON 10-3PRE-ALGEBRA LESSON 10-3
Find the area.
1. Find the exact area of a circle with diameter 32 in.
2. A 5-ft-diameter round table is in a 12 ft-by-15 ft room.
a. What is the area covered by the table? Round to the nearest unit.
b. What is the area of the rest of the room? Round to the nearest unit.
160 ft2
20 ft2
256 in.2
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