Transcript Do Now 5/1/12 - Howell Township Public Schools

Do Now 4/17/13
 Take out HW from last night.
Text p. 362, #1-24 all, 27, 32, 33
 Copy HW in your planner.
Text p. 366, #7-15 all, 24, 29
Text p. 370, #7-17 all
Quiz sections 9.1-9.3 Friday
 In your journal, find the perimeter of the figure
below.
8 cm
10 cm
Homework
Text p. 362, #1-24 all, 27, 32, 33
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1) 18 m
2) 24 in.
3) 32 ft
4) 36 in.
5) 20 m
6) 12 ft
7) 37.7 m
8) 9.4 ft
9) 131.9 in.
10) 140 ft
11) 48 cm
12) 30 ft
13) 44 m
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14) 26 in.
15) 8 ft
16) 36.4 cm
17) 110 cm
18) 18.8 m
19) 32 in.
20) about 29 in.
21) 2.8 m; 5.7 m
22) 13.4 yd; 42.1 yd
23) 5.3 in.; 33.3 in.
24) 1/2; 1
27) 96 ft
32) D
33) 28
Objective
SWBAT find the area of a circle and the
area of irregular figures
Section 9.2
“Area of a Circle”
Area of a Circle
To find the area of a circle, square the radius
of the circle and multiply by pi (  ).
2
Area = r
Radius
Diameter
Try It Out!!
 Find the area of the following circles.
A).
B).

3m
4m
  radius radius
  radius radius
3.14 3  3
3.14 2  2
28.26 m
2
12.56 m 2
Find the area of the shaded region of the
circle. Use 3.14 for  . Round your answer to
the nearest hundredth.
The measurement of the
radius of the circle is 2.4 cm.
A = r2
A = 3.14 · 2.42
2.4 cm
A  3.14 · 5.76
A  18.09
3
of the circle is shaded, divide the area of the
4
circle by 4 and subtract the answer from the entire area.
18.09 ÷ 4 = 4.52. 18.09 – 4.52 = 13.57.
Since
The area of the shaded region of the circle is about
13.57 cm2.
Section 9.3
“Area of Irregular Figures”
Composite Figure
figure that is irregular made up of
simple geometric shapes, such as
triangles, rectangles, and circles
Estimate the area of the figure. Each
square represents 1ft².
Find the area of the figure. Use 3.14 for pi.
Break the figures
apart into simple
shapes: circles,
rectangles, squares,
or triangles. Find the
area for each part.
Then find the sum.
15 m
35 m
Area of
semi-circles
Alw
A  r 2
3.14  7.5
176.6 m 2
Area
of rectangle
2
Total
15 35
176.6 m²
+ 525 m²
525 m 2
701.6 m²
Find the area of the figure.
10 ft
Break the figures apart
into simple shapes:
circles, rectangles,
squares, or triangles. Find
the area of each part.
Then find the sum.
8 ft
Area of
semi-circle
Area of
rectangle
3.14 4
Alw
88
A  r 2
2
50.24  2
25.12 ft 2
64 ft 2
Area of
triangle
A
1
bh
2
1
(8)(10)
2
40 ft 2
Total
25.12 ft²
+ 64 ft²
+ 40 ft²
129.12 ft²
The foul poles down the 1st and 3rd base lines on
a baseball field are 250 feet from home plate. Find
the area of the field.
Break the figures
apart into simple
shapes: circles,
rectangles, squares,
or triangles. Find
the distance around
each part.
Area of
quarter-circle
A  r 2
3.14  2502
196,250  4
49,062.5 ft 2
24
Homework
Text p. 366, #7-15 all, 24, 29
Text p. 370, #9-17 all