1. Monday, 3/20/17
Write the IC and HW in your planner.
IC: Circles – Day 3 (Ch.8)
HW: P #1,3-5,8,9
Materials
Pencil
Slate/marker/eraser
Math folder
Extra Credit PEMDAS
Notes from Friday & today
0:18
0:19
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0:21
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0:27
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0:26
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0:11
0:03
0:04
0:02
0:01
1:00
End
0:05
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0:08
0:07
0:13
0:29
0:51
0:52
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0:49
0:30
0:48
0:53
0:54
0:59
1:00
0:58
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0:55
0:56
0:46
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0:35
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0:37
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0:44
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0:40 1 1 1 1 1

2. Bellwork C  3•d C  3•d C  3•d C  3•2 C  3•4 C  6 cm C  12 cm
Find the approximate circumference for each circle.
1 cm
4 cm
2 cm
C  3•d
C  3•d
C  3•2
C  3•4
C  6 cm
C  12 cm

3. C) Find the approximate circumference of Circle A.
8 units
C  3•d
C  3•8
C  24 units

4. Circumference of Circles
diameter
Circumference  3•diameter
C  3•d
radius

5. Cut the circle into 4 pieces by cutting on the solid black lines.

6. Area of Circles r
½ C r
½ C
Area = ½ C • r

7. A  ½ C • r A  ½ (24) • 4 A  12 • 4 A  48 square units
E. Find the approximate area (use the area formula!!)
8 units
A  ½ C • r
4 units
A  ½ (24) • 4
A  12 • 4
A  48
square units

8. A  ½ C • r C  3•d C  3•18 C  54 in A  27 • 9 A  243 in²
Ex. 1: The diameter of a regulation dart board is 18 in.
Find the approximate circumference.
18 in
9 in
C  3•d
C  3•18
C  54 in
b) Find the approximate area.
A  27 • 9
A  ½ C • r
A  243 in²
A  ½ (54) • 9

9. A  ½ C • r C  3•d C  3(7) C  21 cm A  ½ (21)(3.5) A  36.75 cm²
Ex. 2: The radius of an orange slice is 3.5 cm.
Find the approximate circumference.
3.5 cm
7 cm
C  3•d
C  3(7)
C  21 cm
b) Find the approximate area.
A  ½ C • r
A  ½ (21)(3.5)
A  cm²
A  10.5(3.5)

10. A  ½ C • r C  3•d C  3•26 C  78 in A  39 • 13 A  ½ (78) • 13
Ex. 3: The diameter of a typical adult sized bike wheel is 26 inches.
Find the approximate circumference.
26 in
13 in
C  3•d
C  3•26
C  78 in
b) Find the approximate area.
A  ½ C • r
A  39 • 13
A  ½ (78) • 13
A  507 in²

11. Ex. 4: The radius of one of Saturn’s rings is 125,000 km.
Find the approximate circumference.
250,000 km
125,000 km
C  3•d
C  3(250,000)
C  750,000 km
b) Find the approximate area.
A  ½ C • r
A  ½ (750,000)(125,000)
A  46,875,000,000 km²
A  375,000(125,000)

12. Circumference (distance around)
Object
Diameter
(distance across)
Circumference (distance around)
Ratio
Dart Board
18 inches
56.5 inches
Orange Slice
7 cm
22 cm
Bike wheel
26 in
81.7 in
Saturn’s ring
250,000 km
785,400 km

13. +
3 and a little extra
12 +
3 and a little extra 6 4 2 d C d C