6th Grade
Chapter 7: Multiplying and Dividing Fractions – Homework Feb -12
7.4 Circles and Circumference (p 280)
a) Circumference (C) is the perimeter of a circle.
(Perimeter is the distance around any shape).
b) Diameter (d) is a line through the center of the circle.
1
c) Radius (r) is of the diameter.
2
d) Center Point is the middle of the circle.
1
Since the Radius (r) is x Diameter, the Diameter is also 2r or d =2r.
2
6th Grade
Chapter 7: Multiplying and Dividing Fractions – Homework Feb -12
The formula for Circumference (C)
= 𝝅d or 𝑪 = 𝝅𝟐𝒓.
(The normal format for 𝐶 = 𝜋2𝑟 𝑖𝑠 𝑪 = 𝟐𝝅𝒓 )
𝜋 is a symbol for Pi. It is a nonrepeating decimal.
𝟐𝟐
We approximate 𝜋 to be a value of: 3.14 or
𝟕
Feb 10- Homework: page 282 7-23 Odd.
7) Find the approximate circumference of a circle with a radius of .95 meters.
C = ?,
r=Radius = .95
d = Diameter = 2 * r
𝜋 ≈
value of
3.14 or
𝟐𝟐
d = 2 * .95 = 1.9
𝐶 = 2𝜋𝑟 𝑜𝑟 𝐶 = 𝜋𝑑
C = 2 * 3.14 * .95
or
𝟕
C = 3.14 x 1.9 = 5.96
9) d = 4 : 𝐶 = 𝜋𝑑
𝐶 = 3.14 𝑥 4 = 12.56 ≈ 𝟏𝟐. 𝟔
1
7
11) d = 23 = 3 𝑜𝑟 2.33
𝟐𝟐
7
22
𝐶 = 𝜋𝑑
𝐶 = 3.14 𝑥 2.33 𝑜𝑟 𝐶 = 𝟕 𝑥 3 ≈ 3 = 𝟕
13) r = 6, so d=12: 𝐶 = 𝜋𝑑
𝐶 = 3.14 𝑥 12 = 37.68 ≈ 𝟑𝟕. 𝟕
15) d = 8, so 𝐶 = 𝜋𝑑
𝐶 = 3.14 𝑥 8 = 25.12 ≈ 𝟐𝟓. 𝟏
17) d = 3.1, so 𝐶 = 𝜋𝑑
𝐶 = 3.14 𝑥 3.1 = 9.73 ≈ 𝟗. 𝟕
19) Find the measure of a circumference of a circle that has a diameter of 16.8 centimeters.
𝐶 = 𝜋𝑑
𝐶 = 3.14 𝑥 16.8 = 52.75 ≈ 𝟓𝟐. 𝟖
𝟏
𝟑
1
21) A bike has a large wheel in the front with a radius of 22 feet. How far does the bike travel with each
rotation of the wheel?
1
5
2 𝑜𝑟
2
2
𝑟=
𝐶 = 2𝜋𝑟 𝑜𝑟 𝐶 = 𝜋𝑑:
𝑠𝑜,
𝟏
𝒅 = 𝟐 𝒙 𝟐 = 𝟓 𝒐𝒓
𝟐
𝒅=𝟐𝒙
𝟓
𝟐
=𝟓
𝐶 = 𝜋𝑑 = 3.14 𝑥 5 ≈ 15.7
Or 𝐶
= 2𝜋𝑟 = 2 𝑥
𝟐𝟐
𝟕
𝒙
𝟓
𝟐
=
𝟐 𝒙 𝟐𝟐 𝒙 𝟓
𝟏𝒙𝟕𝒙𝟐
=
𝟏𝟏𝟎
𝟕
= 𝟏𝟓
23) Compare how the circumference of two circles compare if the diameter of 1 circle is twice the
diameter of the other. C= 𝜋𝑑
Use 1 and 2:
3.14 x 1
vs 3.14 x 2 = 3.14 vs 6.28
Use 10 and 20:
3.14 x 10
vs 3.14 x 20 = 31.40 vs 62.8
Use 5 and 10:
3.14 x 5
vs 3.14 x 10 = 15.70 vs 31.4
𝟓
𝟕