Vocabulary
The distance from the center of a circle to the edge is called...
the radius.
If the radius is 5 feet, what is the diameter?
10 feet
What is the formula for circumference?
C = πd
Find the area of a circle with a radius of 6 meters.
A = 113.04 m2
Betsy wants to make an apple pie. She has a 9-inch diameter pie plate for baking. How much filling will she need to cover the entire baking dish?
A = 63.585 in2
Betsy will need at least 63.585 square inches of filling to cover the bottom of the baking dish.
The distance across a circle through the center is called...
the diameter.
What is the radius of a circle with a diameter of 15 millimeters?
7.5 mm
Find the circumference of a circle with a diameter of 12 inches.
C = 37.68 inches
Find the area of a circle with a radius of 25 cm.
A = 1962.5 cm2
Rob wants to put a rim around the edge of his pool. The diameter of the pool is 24 feet. How much of the rim will he need to buy?
Circumference = 75.36 feet.
Rob will need to buy at least 75.36 feet of rim. He should buy more just in case.
Circumference is...
the distance around a circle.
Find the diameter of a circle if the circumference is 25.12 cm. Use 3.14 for pi.
25.12/3.14 = 8
Find the circumference of a circle with a radius of 12 feet.
C = 75.36 feet
Find the area of a circle with a diameter of 14 yards.
A = 153.86 yds2
The earth has a diameter of 7926.41 miles. What is the circumference of the earth?
Circumference = 24888.9274 miles
The amount needed to shade in a circle is...
the area.
How do you find the diameter of a circle if you know the radius?
You multiply the radius by 2 to find the diameter.
Find the circumference of a circle with a radius of 4.25 meters.
C = 26.69 meters
Find the area of a circle with a diameter of 20.5 feet. Round your answer to the nearest tenth.
A = 329.9 ft2
The earth has a diameter of 7926.41 miles. What is the area of the center of the earth? Use a calculator on your Chromebook. Round your answer to the nearest hundredth.
radius = 3963.205 miles
A = 49,319,960.76 miles2
What is the formula for area?
A = πr2
How do you find the radius of a circle if you have the diameter?
You divide the diameter by 2 to find the radius.
Find the radius of a circle with a circumference of 47.1 inches. Use 3.14 for pi.
radius = 7.5 inches
47.1/3.14 = 15 (diameter)
15/2 = 7.5 (radius)
If the area of a circle is 78.5 meters, find the radius. Use 3.14 for pi.
Radius = 5 meters
78.5/3.14 = 25
Then take the square root of 25, which = 5.
Smitty's Pizza has two pizza deals for the same price:
one large 24-inch diameter pizza
OR
two 14-inch diameter pizzas
Which one has the better deal for the customer?
Area of one large pizza = 452.16 in2
Area of two smaller pizzas (one is 153.86 in2 times two pizzas) = 307.72 in2
The 24-inch pizza is the better deal. You get more pizza for the same cost.