Do Now
19
Evaluate. 1. 6 4 2 2. 5.6 2 3 Simplify each expression. 3. 6 + n – 4 4. 5(n + 1) 96 44.8 n + 2 5n + 5 Do Now
description
Do Now. Evaluate . 1. 6 4 2 2. 5.6 2 3 Simplify each expression. 3. 6 + n – 4 4. 5( n + 1). 96. 44.8. n + 2. 5 n + 5. DWP #76. 3/14/ 2013 9-2 D Area of Circles. A ≈ 3 • 20 2. A ≈ 3 • 400. A ≈ 1,200 m 2. Example 1 - PowerPoint PPT Presentation
Transcript of Do Now
Evaluate.
1. 6 42
2. 5.6 23
Simplify each expression.
3. 6 + n – 4
4. 5(n + 1)
96
44.8
n + 2
5n + 5
Do Now
4/15/2015 9-2 D Area of Circles
Example 1
Estimate the area of the circle. Use 3 to approximate .
A ≈ 3 • 202
A ≈ 1,200 m2
A = r2
A ≈ 3 • 400
Example 2
Estimate the area of the circle. Use 3 to approximate .
r = 28 ÷ 2
A ≈ 3 • 142
A = r2
r = 14
r = d ÷ 2
A ≈ 3 • 196
A ≈ 588 m2
Example 3
Find the area of the circle. Use for .
A = r2
r = d ÷ 2r = 8 ÷ 2 = 4
A • 16 22
7 __
A 50 ft2
22 7
A • (4)222
7352
72 7
Example 4
Find the area of the circle. Use for .
A = r2
A • 4922
7 __ 7
A 154 cm2
22 7
A • 7222
7
1
Example 5
A drum head has a radius of 18 in. Find the area of the material covering the drum head. use 3.14 for .
A 3.14 • 182
18 in.A = r2
A 3.14 • 324
A 1,017.36 in.2
Example 6Find the area of the circle.Use 3.14 for .
Estimate 3 × 4 × 4 = 48
A = r2
A ≈ 3.14 ● 42
A ≈ 3.14 ● 16
A ≈ 50.24
The area of the circle is approximately 50.24 square centimeters.
Check for Reasonableness 50.24 ≈ 48
Example 7Find the area of the fountain shown. Use 3.14 for . Round to the nearest tenth if necessary.
Estimate 3 × 3 × 3 = 27
A = r2
A ≈ 3.14 ● 2.62
A ≈ 3.14 ● 6.76
A ≈ 21.2
The area is approximately 21.2 square meters.
Example 8Find the area of the semicircle. Use 3.14 for . Round to the nearest tenth if necessary.
Replace r with 4.5
The area of the semicircle is approximately 31.8 square centimeters.
A ≈ 0.5(3.14)(4.5)2 Use 3.14 for .
A ≈ 0.5(3.14)(20.25) 4.52 = 4.5 ● 4.5 = 20.25
A ≈ 31.8 Simplify.
Estimate the area of each circle.
1. 2.
27 km2
1,200 yd2
Exit Ticket
3. 4.
4.53 cm2 1.54 m2
Find the area of each circle. Use for .22 7
5. A coater has a diameter of 6 inches. Find the area of the largest cup the coaster can hold. Use 3.14 for .28.26 in2
1. Estimate the area of the circle. Use 3 for .
A. 48 km2 B. 46 km2
C. 44 km2
D. 42 km2
4 km
2. Estimate the area of the circle. Use 3 for .
A. 772 yd2 B. 872 yd2
C. 972 yd2
D. 992 yd2
36 yd
3. Estimate the area of the circle. Use 3 for .
A. 36.75 cm2 B. 21 cm2
C. 10.5 cm2
D. 9.19 cm2
3.5 cm
4. A circular table has a diameter of 8 feet. Identify the area of the table cloth needed to cover the table. Use 3.14 for .
A. 25.12 ft2 B. 37.68 ft2
C. 40.82 ft2
D. 50.24 ft2
Homework
• Pg. 553 #1-20 All• Study for Ch. 9 Quiz II
