Formulas (Buzzer)
What characteristic of a circle can be determined by multiplying the diameter by pi?
Circumference
Given a circle with a radius of 7, what is the circumference? Express your answer using pi = 3.14
C = 43.96
What is the area of a quarter circle that has a radius of 6 units?
A full circle with a radius of 6 units would have an area of A = πr2 = π x 62 = 36π
Since this is a quarter circle, divide the answer by 4.
The area would be 9π, or 28.26 units
Since we are covering the yard, we need to find the area of the yard.
Area = π x radius2 = π x 122 = 144π, or 452.16 square feet. Since each bag covers 5 square feet, divide 452.16 by 5 to get 90.32.
Alex needs 91 bags to cover his yard.
Before Mt. Everest was discovered, what was the tallest mountain on the planet Earth?
Mt. Everest (it just wasn't discovered yet, but it still existed)
What characteristic of a circle can be determined by multiplying the radius by radius by pi?
Area of a circle
If the circumference of a circle is 144π, what is the radius?
Determine the area of a circle that has a radius of 8.
Area = 64π or Area = 200.96
Samantha wants to build a fence around her concrete patio which surrounds a circular pool. If the pool has a radius of 14 feet, and there is an additional 8 feet wide patio of concrete around the entire pool, how many feet of fence will Samantha need to surround the patio and pool?
If the radius of the pool is 14 feet, then the pool has a diameter of 28 feet. Since there is also an 8 feet wide concrete patio around the pool, that means the pool total diameter is 28 + 8 + 8 (because there is 8 feet on both sides).
The total diameter is 44 feet, making the circumference 44π, or 138.16 feet squared.
Someone who has Anatidaephobia has a phobia of what?
The irrational belief that a duck (or goose/swan) is constantly watching you.
The diameter is equal to the radius times _______.
Two
True or False: The Circumference of a circle represents the space inside the circle.
False. Area is inside the circle. Circumference is AROUND a circle.
If the area of a circle is 81π, what is the circumference? Write your answer in terms of π
A = π x radius x radius.
81π = π x radius2, meaning the radius is 9 (9x9=81)
Circumference = 2πr = 2 x π x 9 = 18π
The answer is 18π
Scarlett incorrectly believes the area of a circle with a radius of 9 is equal to 18π. What was her mistake? What is the correct answer?
Instead of calculating 92, Scarlett did 9 x 2 to get 18.
The correct answer is 81π, or 254.34 square units
What was Mickey Mouse's original name?
Mortimer Mouse
Determine if the following statements represents radius, diameter, circumference, or area.
1) The distance from the middle of a round plate to the edge.
2) The metal rim of a basketball hoop.
3) The amount of paint needed to paint a circular counter top.
1) Radius (from middle to edge)
2) Circumference (a metal rim has a circular edge)
3) Area (covering a circular surface)
If the circumference of a circle is 26π, what is the radius?
radius = 13
Determine the area of a semi-circle that has a diameter of 12.
The radius is 6, meaning the area of a full circle is 36π.
Since this is a semi-circle, which is half a full circle, the area = 18π
Michael is standing in the middle of a circular field and throws a football to the edge of the field. The football traveled 50 yards. What is the circumference of the field? Use 3.14 for pi.
Since Michael is in the middle and threw the football to the edge, then 50ft is the radius.
To find circumference, C = 2 x 3.14 x 50 = 100 x 3.14 = 314.
The field has a circumference of 314 yards
What is the only number in the English language that is spelt with the same amount of letters as the number itself?
4 has four letters
F - O - U - R
Write an equation to determine the Area of a semi circle.
Area = (π x r2) / 2
Circle A has a radius of 12 inches. Circle B has a diameter of 20 inches. Which circle has a greater circumference? Show your work.
Circle A has a radius of 12. C = 2πr = 2 x π x 12 = 24π
Circle B has a diameter of 20. C = πd = π x 20 = 20π
Circle A has a greater circumference because 24π is greater than 20π
Determine the area of a quarter circle that has a radius of 5.
If it were a full circle, area = 5 x 5 x π which equals to 25π
Since this is a quarter circle, divide the area by 4.
The correct answer is A = 6.25π
There are 12 eggs in a carton. 12 people take one egg each, but there is still one egg in the carton. How is this possible?
The last person left the egg in the carton.
What kind of animal is Squidward from Spongebob Squarepants?
Despite his name, he’s actually an octopus