1. HW: p.345(9-11), p.347(18-20) Materials
Thursday, 3/23/17
Write the IC and HW in your planner.
IC: Ch. 8 Circles – day 5
HW: p.345(9-11), p.347(18-20)
Show all work!
Materials
Pencil & grading pen
Slate/marker/eraser
Math folder
HW due today (Circumference & Area #2) 1 1 1 1 1

2. The circumference of a regulation NCAA men’s basketball must be 29
The circumference of a regulation NCAA men’s basketball must be inches. What would be the diameter of the basketball?

3. Bell-Work Mystery Comic x
In Timothy’s book collection, he has 5 science fiction books, 6 comic books, and 4 mystery books. During the fourth quarter, Timothy wants to pick two books to read. What is the probability of him choosing a mystery book and then a comic book ? (Being the typical 7th grader, he picked the 1st book, chucked it on his floor, and then picked the 2nd book.)
1st Pick nd Pick
Mystery
Comic x

4. Bell-Work Blue Red x 1st Pick 2nd Pick
A bag of marbles contains 3 red, 4 blue, and 7 green marbles. With replacement, what is the probability of selecting a blue marble and then a red marble?
1st Pick nd Pick
Blue
Red x

5. "...in terms of pi" 9 in = r 9 in 18 in = d
Ch. 8.1 & State Standard 7.G.4
Objective: TSWBAT discover the other area formula for circles and leave answers in terms of pi.
Date ______________________
"...in terms of pi"
Example 1: What is the circumference of a circle with a radius of 9 inches? Write your answer in terms of pi.
C =  d
9 in = r
C =  (18)
9 in
18 in = d
C = 18 
inches

6. "...in terms of pi" 6 in = d 6 in 3 in = r
Example 2: What is the area of a circle with a diameter of 6 inches? Use 3.14 for pi.
6 in = d
A = ½ C  r
6 in
3 in = r

7. d = 2 d =6 d = 14 d = 20 r = 1 r = 3 r = 7 r = 10 radius C = d
diameter
d = 2
d =6
d = 14
d = 20
radius
C = d
A = ½C•r
r = 1
r = 3
r = 7
r = 10
C = 2
C = 6
C =
14
C =
20
C = •2 14 20 6
½ (2)•1
½ (6)•3
½ (14)•7
½(20)•10
1 • 1
3 • 3
7 • 7
10 • 10
A = 1
A = 9
A =
49
A =
100
A = r² • 
= r²
Shortcut formula for area: ________________

8. "...in terms of pi" 6 in = d 6 in 3 in = r
Example 2: What is the area of a circle with a diameter of 6 inches? Write your answer in terms of pi.
6 in = d
A =  r²
6 in
A =  (3²)
3 in = r
A = 9 
A = 9  in²

9. Find the area in terms of pi:
Now it's time for...
SLATES!
Slates 1:
16 ft
Find the circumference a) in terms of pi and b) using 3.14 for pi.
a) C = 16 ft
b) C ≈ ft
Slates 2:
5 in.
Find the area in terms of pi:
A = 25 in²

10. Slates again! Woo-hoo! Slates 1:
A circular swimming pool has a diameter of 10 meters. How much area of the backyard does the pool cover?
Area or Circumference?
Draw a picture:
Slates 2:
The circular lid for a jar has a radius of 4 centimeters. What is the circumference of the lid?
Area or Circumference?
Draw a picture:

11. Closure
A seventh grade student completed this math problem:
On your slate, identify what the student’s mistake was in finding the area of the circle.

12. p.345
p.347