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If this circle has actually a diameter that 12 inches, what is its circumference?

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*


*


*


*


Explanation:

Know that the formula because that circumference is 

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, wherein C is the circumference and D is the diameter. That is given that the diameter is 12 inches. Therefore, the circumference is 
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A circle is circumscribed about a square that has sides the 5cm. What is the perimeter the the circle?


Explanation:

Because the circle is circumscribed roughly the square, the diagonal line of the square is the very same as the diameter the the circle. So to discover the diagonal we use the Pythagorean Theorem:

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So the equation to settle becomes

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or
*

The perimeter, or circumference, of the circle is offered by

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or
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Find the perimeter the the ice cream rink formed by the rectangle and also semi-circles with the dimensions shown.

You are watching: Find the circumference of a circle whose area is


Explanation:

The perimeter the the rink runs follow me the external of the an unified shapes. The two external edges the the rectangle are 

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each, so 
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that the perimeter is composed of those two sides.

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The 2 semi-circles that type the remainder the the perimeter, and can be taken into consideration two halves the one circle. The diameter that the circle would certainly be 

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. The circumference of the circle would account because that the external edges that the 2 semi-circles in the ice rink. Find the circumference of the circle v the formula 
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as follows.

*

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Finally, include this circumference that accounts for the semi-circles come the size of the two sides created by the rectangle to find the full perimeter that the rink.

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*


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Example question #1 : how To discover Circumference


If a circle has actually an area the

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, what is the circumference the the circle?


Possible Answers:
Correct answer:

*


Explanation:

The formula for the area the a one is πr2. For this particular circle, the area is 81π, so 81π = πr2. Division both sides by π and we are left with r2=81. Take it the square root of both sides to discover r=9. The formula because that the one of the circle is 2πr = 2π(9) = 18π. The correct answer is 18π.


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Example concern #3 : exactly how To uncover Circumference


A circle with an area of 13π in2 is focused at allude C. What is the circumference of this circle?


Possible Answers:

√13π


26π


2√13π


13π


√26π


Correct answer:

2√13π


Explanation:

The formula because that the area that a circle is πr2.

We are provided the area, and by substitution we recognize that 13π πr2.

We division out the π and are left through 13 = r2.

We take it the square root of r to find that r = √13.

We discover the one of the circle with the formula = 2πr.

We then plugin our worths to uncover = 2√13π.


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Example concern #1 : just how To uncover Circumference


A 6 through 8 rectangle is inscriptions in a circle. What is the circumference of the circle?


Possible Answers:

12π


10π


25π


8π


6π


Correct answer:

10π


Explanation:

First you must draw the diagram. The diagonal of the rectangle is additionally the diameter the the circle. The diagonal line is the hypotenuse of a lot of of 2 the a 3,4,5 triangle, and also therefore is 10. One = π * diameter = 10π.


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Example concern #1 : how To find Circumference


A gardener wants to develop a fence approximately their garden displayed below. How numerous feet the fencing will they need, if the size of the rectangle-shaped side is 12 and also the broad is 8?

 
  

 

 

 

 


Possible Answers:

8π + 24


4π + 24


96 ft


40 ft.


Correct answer:

8π + 24


Explanation:

The form of the garden is composed of a rectangle and two semi-circles. Because they are structure a fence we require to discover the perimeter. The perimeter of the length of the rectangle is 24. The perimeter or circumference of the circle can be found using the equation C=2π(r), whereby r= the radius that the circle. Due to the fact that we have two semi-circles we can find the one of one entirety circle through a radius the 4, which would certainly be 8π.

 

 

 

 


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Example concern #6 : just how To uncover Circumference


The diameter the a circle is characterized by the two points (2,5) and (4,6). What is the circumference of this circle?


Possible Answers:


2.5π


π√2.5


π√5


None the the various other answers


Correct answer:

π√5


Explanation:

We an initial must calculate the distance between these 2 points. Recall the the street formula is:√((x2 - x1)2 + (y2 - y1)2)

For us, the is therefore: √((4 - 2)2 + (6 - 5)2) = √((2)2 + (1)2) = √(4 + 1) = √5

If d = √5, the circumference of ours circle is πd, or π√5.


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Example concern #4 : how To uncover Circumference


The diameter that a circle is 16 centimeters. What is the one of the circle?


Possible Answers:
Correct answer:

*


Explanation:

To uncover the one of a circle, main point the circle"s diameter through pi (3.14).

See more: What Is 5/9 As A Decimal ? How Do You Convert 5/9 To A Decimal

 

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Example inquiry #5 : exactly how To find Circumference


A auto tire has a radius the 18 inches. Once the tire has actually made 200 revolutions, how far has the vehicle gone in feet?


Possible Answers:

3600π


600π


300π


500π


Correct answer:

600π


Explanation:

If the radius is 18 inches, the diameter is 3 feet. The one of the tire is as such 3π by C=d(π). After ~ 200 revolutions, the tire and also car have gone 3π x 200 = 600π feet.


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