Calculate Circle Radius from Circumference 31.41: Using C = 2πr

A circle has a circumference of 31.41.

What is its radius?

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Step-by-step video solution

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00:00 Find the radius
00:03 We'll use the formula for calculating circle circumference
00:09 We'll substitute appropriate values according to the given data and solve for the radius
00:15 We'll substitute the value of pi
00:29 We'll isolate radius R and calculate
00:43 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

A circle has a circumference of 31.41.

What is its radius?

2

Step-by-step solution

To solve the exercise, first we must remember the circumference formula:

P=2πR P= 2\pi R

P is the circumference and Pi has a value of 3.14 (approximately).

We substitute in the known data:

31.41=2⋅3.141⋅R 31.41=2\cdot3.141\cdot R

Keep in mind that the result can be easily simplified using Pi:

31.413.141=2R \frac{31.41}{3.141}=2R

10=2R 10=2R

Finally, we simplify by 2:

5=R 5=R

3

Final Answer

5

Practice Quiz

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A circle has a radius of 3 cm.

What is its perimeter?

333

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