How to find the circumference of a circle in pre-algebra - Math
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An ant is standing at the center of a perfectly circular plate. If the ant crawled in a straight line, he would have to crawl 6 inches to reach the edge of the plate. How many inches would he crawl if he crawled a full circle around the edge of the plate?
An ant is standing at the center of a perfectly circular plate. If the ant crawled in a straight line, he would have to crawl 6 inches to reach the edge of the plate. How many inches would he crawl if he crawled a full circle around the edge of the plate?
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We need to find the circumference:
In this formula 
stands for the radius and 
stands for the diameter.
The distance the ant must crawl to the edge from the center is the radius of the circle.
Plug in 6 inches for 
:
We need to find the circumference:
In this formula
The distance the ant must crawl to the edge from the center is the radius of the circle.
Plug in 6 inches for
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If a circle has a radius of 
meters, what is its circumference?
If a circle has a radius of
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The formula for the circumference of a circle is 
, where 
is the diameter. This can also be written as 
, where 
is the radius of the circle. We were given the radius, so we take the second formula and plug in 
for 
.
The formula for the circumference of a circle is
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Find the circumference of a circle with a radius of 6 inches.
Find the circumference of a circle with a radius of 6 inches.
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Use the circumference formula 
and plug in 6 for 
. Leave 
in your answer to get 
.
Use the circumference formula
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If the circumference of a circle is 
, what is the radius of the circle?
If the circumference of a circle is
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The formula for the circumference of a circle is 
.
The problem gives us the circumference, so plug that in:
Notice that the 
's cancel out:
Divide both sides by 
:
The formula for the circumference of a circle is
The problem gives us the circumference, so plug that in:
Notice that the
Divide both sides by
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
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To find the circumference of a circle given the radius we must first know the equation for the circumference of a circle which is
We then plug in the number for the radius into the equation yielding
We multiply to find the value for the circumference is 
.
The answer is 
.
To find the circumference of a circle given the radius we must first know the equation for the circumference of a circle which is
We then plug in the number for the radius into the equation yielding
We multiply to find the value for the circumference is
The answer is
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
To find the circumference of a circle given the radius we must first know the equation for the circumference of a circle which is
We then plug in the number for the radius into the equation yielding 
We multiply to find the value for the circumference is 
.
The answer is 
.
To find the circumference of a circle given the radius we must first know the equation for the circumference of a circle which is
We then plug in the number for the radius into the equation yielding
We multiply to find the value for the circumference is
The answer is
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
To find the circumference of a circle given the radius we must first know the equation for the circumference of a circle which is
We then plug in the number for the radius into the equation yielding
We multiply to find the value for the circumference is 
.
The answer is 
.
To find the circumference of a circle given the radius we must first know the equation for the circumference of a circle which is
We then plug in the number for the radius into the equation yielding
We multiply to find the value for the circumference is
The answer is
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What is the circumference of a circle with radius 
?
What is the circumference of a circle with radius
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Remember, the formula for circumference of a circle is 
.
Plug in our given values:
Remember, the formula for circumference of a circle is
Plug in our given values:
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If the circumference of a circle is 
, what is the diameter of the circle?
If the circumference of a circle is
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The diameter of the circle is twice the radius, or 
. We first need to find the radius using the information that has been given to us.
The formula for the circumference of a circle is 
.
The problem gives us the circumference, so plug that in:
Notice that the 
's cancel out:
Divide both sides by 
:
Plug that into our first equation:
The diameter of the circle is twice the radius, or
The formula for the circumference of a circle is
The problem gives us the circumference, so plug that in:
Notice that the
Divide both sides by
Plug that into our first equation:
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If the diameter of a circle is 
, what is the circumference?
If the diameter of a circle is
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The formula for circumference is 
. The problem gives us the diameter instead of the radius, so we need to convert.
The diameter is twice the radius or 
.
This means that, for this circle, 
.
Divide both sides by 
:
Plug this value into our initial equation to solve:
The formula for circumference is
The diameter is twice the radius or
This means that, for this circle,
Divide both sides by
Plug this value into our initial equation to solve:
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
To find the circumference of a circle we must first know the equation for the circumference of a circle, which is 
.
We then plug in the given value for the radius, yielding 
.
We multiply to find the value for the circumference is 
.
Thus answer is 
.
To find the circumference of a circle we must first know the equation for the circumference of a circle, which is
We then plug in the given value for the radius, yielding
We multiply to find the value for the circumference is
Thus answer is
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
The formula for circumference of a circle is 
.
Plug in our given information and solve.
The formula for circumference of a circle is
Plug in our given information and solve.
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
The formula for circumference of a circle is 
.
Plug in our given values.
The formula for circumference of a circle is
Plug in our given values.
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What is the circumference of a circle with radius of 
?
What is the circumference of a circle with radius of
Tap to reveal answer
The formula for circumference of a circle is 
.
Plug in our given values.
The formula for circumference of a circle is
Plug in our given values.
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
The formula for circumference of a circle is 
.
Plug in our given values.
The formula for circumference of a circle is
Plug in our given values.
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
The formula for the circumference is 
.
Plug in our given radius and solve.
The formula for the circumference is
Plug in our given radius and solve.
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
To find the circumference of a circle given the radius, we must first know the equation for the circumference of a circle which is
We then plug in 
for the radius into the equation yielding
We multiply to find the value for the circumference is
The answer is 
.
To find the circumference of a circle given the radius, we must first know the equation for the circumference of a circle which is
We then plug in
We multiply to find the value for the circumference is
The answer is
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Find the circumference of a circle with a diameter of 4 meters.
Find the circumference of a circle with a diameter of 4 meters.
Tap to reveal answer
The formula for circumference is:
where 
is the radius of our circle
In this case, we were given the diameter of 
meters. Thus, we know that the radius is 
meters (since the diameter is twice the radius). Plugging this into the formula, we have:
meters.
The formula for circumference is:
In this case, we were given the diameter of
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
To find the circumference of a circle, use the equation:
Substitute the given value for the radius into the equation:
To find the circumference of a circle, use the equation:
Substitute the given value for the radius into the equation:
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What is the circumference of a circle with a radius of 
?
What is the circumference of a circle with a radius of
Tap to reveal answer
The formula for the circumference of a circle is 
.
Plug in our given values and solve.
The formula for the circumference of a circle is
Plug in our given values and solve.
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