Geometry Help

Circumference the Circle

Understanding what the one of a circle is, as well as how to calculate the one of a one is a reasonably easy geometry principle. By adhering to the one problems and also solutions in the Geometry assist Online ar below, you should easily be able master the ide of circumference.

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By following along with the examples given and taking the digital Math do Easy! geometry quiz because that circumference of a circle, girlfriend will have the ability to complete her geometry homework ~ above this topic in a snap.

Circumference of one Formula

The one of a one is simply the distance around a circle. Sometimes it is described as the perimeter, back the hatchet perimeter is usually reserved for the measure up of a distance approximately a polygon.

The equation for the one of a circle deserve to be created in two ways:

C = 2πrC = πd

Where: r to represent the radius the the circle and d represents a circle's diameter.

Recall the the radius is the distance from the facility of the circle come a suggest on the sheet of a circle and also the diameter is the largest distance throughout a circle. The diameter is always twice the size of the radius.

When calculating the circumference v a recognized radius usage the very first version that the one formula shown; as soon as the diameter is known use the second version that the circumference formula shown.

Modern Day supplies for Circumference

Did you understand that the one of the earth was very first calculated more than 2200 years back by the Greek mathematician, Eratosthenes?

Knowing exactly how to calculation circumference is used in many fields of study, including:


High college Geometry aid - Terms

Circle terms to Know:

Pi: symbol because that pi is π and it equals about 3.14Radius: The distance from the facility of a circle to an edgeRadii: The plural because that radius.Diameter: The street from one edge of a circle to one more edge going with the center.Circumference: The distance approximately a circle; the perimeter of a circle.

Math do Easy! Tip

If you have actually trouble mental geometry terms, it help to think of other words from the exact same root with which you might be an ext familiar.

For example, the Latin source of the word circumference is circum, meaning around. Circum is now taken into consideration a prefix also meaning around or round about.

Here is a perform of words the come native the root/prefix circum that can assist you remember the circumference the street of measure approximately a circle:

Circus - (from the source circum) usually hosted in a circular arenaCircle - (from the source circum) a round shapeCircumvent - to walk around or bypass; come avoidCircumstances - conditions surrounding and eventCircumnavigate - to paris or sail around



Geometry assist Online: Circumference

Check out 4 common types of geometry homework problems and solutions involving the circumference of circles.

Math do Easy! Quiz - Circumference

For each question, choose the ideal answer. The answer crucial is below.

What is the circumference of a circle with a radius that 1 cm.?2 cm.6.28 cm.3.14 cm.What is the one of a circle through a diameter the 7 ft.?21.98 ft.43.96 ft.14 ft.Find the circumference of a circle v an area the 153.86 cm. Squared.7 cm.43.96 cm.49 cm.

Answer Key

6.28 cm.21.98 ft.43.96 cm.

#1 find the one of a Circle given the Radius

Problem: uncover the circumference of a circle with a radius of 20 cm.

Solution: plugin 20 for r in the formula C = 2 πr and solve.

C = (2)(π)(20)C = 40πC = 125.6

Answer: A circle through a diameter that 20 cm. Has a one of 125.6 cm.

#2 discover the one of a Circle offered the Diameter

Problem: Find the circumference of a circle v a diameter of 36 in.

Solution: Simply plug in 36 for d in the formula C = πd and solve.

C = (π)(36)C = (3.14)(36)C = 113

Answer: The circumference of a circle v a diameter of 36 in. Is 113 in.

#3 uncover the Radius that a Circle offered the Circumference

Problem: What is the radius the a circle with a one of 132 ft.?

Solution: Since we are trying to determine the radius, plugin the known circumference, 132, for C in the formula C = 2πr and also solve.

132 = 2πr66 = πr (divide both political parties by 2)66 = (3.14)rr = 21 (divide both political parties by 3.14)

Answer: A circle with a circumference of 132 ft. Has actually a radius of around 21 ft.

#4 discover the one of a Circle provided the Area

Problem: find the one of a circle that has an area of 78.5 m. Squared.

Solution: This is a two-step problem. First, because we understand the area that the circle us can figure out the radius that the one by plugging in 78.5 because that A in the area that a circle formula A = πr2 and also solving:

78.5 = πr278.5 = (3.14)r225 = r2(divide both political parties by 3.14)r = 5 (take the square source of both sides)

Now the we know the radius is equal to 5 m. We have the right to substitute 5 in because that r in the formula C = 2πr and solve:

C = 2π(5)C = (2)(3.14)(5)C = 31.4

Answer: A circle with an area that 78.5 m. Squared has a one of 31.4 m.

Do girlfriend need an ext geometry help online?

If you still need assist with various other geometry problems about the circumference of a circle, please ask in the comment ar below. I'll be glad to help out and also may even include circumference math difficulty in the problem/solution ar above.

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unknown on march 13, 2018:

thank you so much this short article was so useful i very much thank you!

Kristin Trapp (author) native Illinois on march 06, 2012:

I'm glad to assist SmartAndFun.

SmartAndFun from Texas on in march 06, 2012:

LOL, my daughter (the smarter one) figured the out. I am complying with you so that I'll be sure to have the ability to find you again. Dd is doing fairly OK in geometry this semester, yet last semester (algebra) most of her homework sessions ended in tears. She acquired a 45 on one algebra assignment the she, mine husband and I all worked on with each other for three hours. LOL, we thought between the three of us she'd get at least a C. We will need you again because that sure! say thanks to you!