Vocabulary
A straight line from the center to the circumference of a circle or sphere
Radius
What is the circumference of a circle if:
the radius = 7 yds?
43.96 or 14π yds
When I need a circumference Ill just use pi d.
radius = 7
7 * 2 = 14
14 is diameter
14 * pi is 14 pi or 43.96
What is the formula to find the area of a circle?
A=
pir^2
What is the area of a circle if:
the Radius = 6 in
36π or 113.04 in2
6 * 6 * 3.14
36 pi or 113.04
What is the diameter of a circle whose circumference is 314?
100
314 / 3.14
Name the line in a circle that cuts it in half.
Diameter
A diameter goes across the circle passing through the middle.
What is the circumference of a circle if:
the radius = 9 yds?
56.52 or 18π yds
radius = 9
9 * 2 = 18 which is the diameter
18 * pi is circumference or 18 * 3.14
18pi or 56.52
What day is Pi Day?
March 14.
3/14
3.14 because the first digits of pi are 3.14
What is the area of a circle if:
the Radius = 3 ft
9π or 28.26 ft2
3 * 3 * 3.14
What is the diameter of a circle whose circumference is 690?
219.63
690 /3.14
The outside measurement of a circle. Or the distance around the outside of the circle
Circumference
Circumference is the perimeter of a circle.
What is the circumference of a circle if:
the diameter is 16.8 yards?
52.75 or 16.8π yds
diameter = 16.8
16.8 pi
16.8 * 3.14 = 52.752
Find the area of a circle when the circumference is 28.26 feet.
63.59 ft2
28.26 / 3.14 = 9 This is the diameter
9/2 = 4.5 this is the radius
4.5 * 4.5 * 3.14 = 63.585
What is the area of a circle if:
the Diameter = 12 feet?
36π or 113.04 ft2
12/2 = 6
6 * 6 * 3.14
What is the radius of a circle whose circumference is 901?
14.49
901 / 3.14 =28.98
28.98 / 2 = 14.49
The measurement of the inside of a circle. Or how much the circle covers
Area
What is the circumference of a circle if:
the radius = 7.4 yds?
46.47 or 14.8π yds
7.4 * 2 = 14.8 which is the diameter
14.8 pi or 14.8 * 3.14 is the circumference
46.47 or 14.8π yds
What is the Area of a circle if the circumference is 43.96?
153.86
43.96 /3.14 = 14 Circumfence / pi is diameter
14/2 = 7 diameter / 2 is radius
7 * 7 * 3.14 = 153.86 pi r2 is area.
153.86
What is the area of a circle if:
the diameter = 8 in
16π or 50.24 in2
8/2 = 4
4 * 4 * 3.14
What is the radius of a circle whose circumference is 372?
59.24
372 / 3.14 = 118.47
118/47 /2 = 59.24
What radius will make the circumference and area equal?
r = 2
Pi r ^ 2 = pi d diameter = 2r
Pi r^2 = pi 2 r divide both sides by pi
r^2 = 2r divide both sides by r.
r = 2
The circular fountain in front of the courthouse has a radius of 9.4 feet. What is the circumference of the fountain to the nearest foot?
59
9.4 * 2 = 18.8
18.8 * 3.14 = 59.032
Which rounds to 59.
A rose garden is circular. The diameter of the garden is 18 feet. Find the total area of the garden using 3.14 for pi.
254.34
18 /2 = 9 this is the radius
9 * 9 * 3.14
254.34
A dog is leashed to a point in the center of a large yard, so the area the dog is able to explore is circular. The leash is 20 feet long. What is the area of the region the dog can explore?
1256
r = 20
20 * 20 * 3.14
a circle is inside a square so that it touches all 4 sides in the center. The side length of the square is 8. What is the area of the part of the square that does not include the circle.
area of the square = 8 * 8 = 64
Radius of the circle would be 4.
Area of the circle is 4 * 4 * 3.14 = 50.24
64 - 50.24 = 13.76