How to find the area of a circle in pre-algebra - Math

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Question

What is the area of circle with a radius of ?

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Answer

To find the area of a circle, use the equation:

$Area=\pi(radius^{2})$

Substitute the given value for radius:

$Area=\pi(7^{2})$

$Area=49\pi$

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Question

What is the area of a circle with diameter ?

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Answer

The area of a circle is calculated with the equation $A=\pi r^2$ .

is half of the diameter, which in our case is 3.

$A=\pi r^2= (3)^2\pi=9\pi$

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Question

Find the area of a circle with a radius of 12 inches.

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Answer

The formula for the area of a circle is $A=\pi r^2$ .

Plug your radius value in and you get $144\pi$ .

Make sure your units are squared.

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Question

Find the area of a circle with a radius of 7 inches.

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Answer

Use the formula for the area of a circle, $A=\pi r^{2}$ , and plug in 7 for the radius to get $49\pi$ . Make sure your answer is in units squared.

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Question

What is the area of circle with a radius of ?

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Answer

To find the area of a circle you must plug the radius into in the following equation

In this case the radius is so we plug it into to get $9^{2}=81$

We then multiply it by $\pi$ to get our answer $A=81\pi$ .

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Question

What is the area of a circle with radius of ?

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Answer

The formula for the area of a circle is $A=\pi r^2$ .

Plug in our given values:

$A=\pi r^2$

$A=\pi*3^2$

$A=9\pi$

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Question

What is the area of a circle with a radius of ?

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Answer

The formula for the area of a circle is $A=\pi r^2$ .

Plug in the information given and solve:

$A=\pi * 4^2$

Remember, a number squared is just the same as that number times itself:

$A=\pi(44)$

$A=16\pi$

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Question

If the area of a circle is $64\pi$ , what is the radius of the circle?

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Answer

The formula for the area of a circle is $A=\pi r^2$ .

Plug in the information given and solve:

$64\pi = \pi r^2$

Notice that the $\pi$ 's cancel out:

Take the square root of both sides:

$\sqrt{64}=\sqrt{r^2}$

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Question

If the diameter of a circle is , what is the area of that circle?

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Answer

The area of a circle is $A=\pi r^2$ , but the problem gives us the diameter and not the radius.

The diameter is twice the radius, so . We can plug in our given values to find the radius:

$\frac{22}{2}=r$

Now we can plug this value into our equation for area:

$A=\pi r^2$

$A=\pi11^2$

$A=\pi 121$

$A=121\pi$

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Question

If the area of a circle is $36\pi$ , what is the length of the radius?

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Answer

The formula for the area of a circle is $A=\pi r^2$ . Plug in our given information to solve:

$A=\pi r^2$

$36\pi=\pi r^2$

The $\pi$ 's cancel out, leaving us with:

Take the square root of both sides:

$\sqrt{36}=\sqrt{r^2}$

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Question

What is the area of a circle with a radius of ?

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Answer

To find the area of a circle, you must plug the radius in for in the following equation:

In this case the radius is , so we plug in for to get $A=\pi(4^{2})$ .

$A=16\pi$

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Question

What is the area of a circle with a radius of ?

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Answer

The formula for area of a circle is $A=\pi r^2$ .

Plug in our given information:

$A=\pi*5^2$

$A=25\pi$

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Question

What is the area of a circle with a radius of ?

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Answer

The formula for area of a circle is $A=\pi r^2$ .

Plug in our given information:

$A=\pi 6^2$

$A=36\pi$

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Question

What is the area of a circle with a diameter of ?

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Answer

The formula for area of a circle is $A=\pi r^2$ . However, the problem gives us the diameter instead of the radius. The diameter is twice the length of the radius:

$\frac{22}{2}=r$

We can plug that back into our area equation:

$A=\pi r^2$

$A=\pi *11^2$

$A=121\pi$

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Question

What is the area of a circle with a diameter of ?

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Answer

The formula for area of a circle is $A=\pi r^2$ . However, the problem gives us the diameter instead of the radius. The diameter is twice the length of the radius:

$\frac{12}2{}=r$

We can plug that back into our original equation and solve:

$A=\pi r^2$

$A=\pi *6^2$

$A=36\pi$

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Question

What is the area of a circle with a radius of ?

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Answer

The formula for the area of a circle is $A=\pi r^2$ .

Plug in our given radius.

$A=\pi r^2$

$A=\pi *2.5^2$

$A=6.25\pi$

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Question

What is the area of a circle with a radius of ?

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Answer

The formula for the area of a circle is $A=\pi r^2$ .

Plug in our radius.

$A=\pi r^2$

$A=\pi 8^2$

$A=\pi64$

$A=64\pi$

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Question

What is the area of a circle with a diameter of ?

Tap to reveal answer

Answer

The formula for area of a circle is $A=\pi r^2$ , but the problem gives us the diameter and not the radius.

The diameter is twice the radius, so . Therefore .

Plug this value into our given equation.

$A=\pi r^2$

$A=\pi (7)^2$

$A=\pi *49$

$A=49\pi$

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Question

What is the area of a circle with diameter of ?

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Answer

The formula for the area of a circle is $A=\pi r^2$ .

The problem gives us the diameter, however, and not the radius. Since the diameter is twice the radius (), then if the diameter is , the radius will be .

Plug that into our given equation.

$A=\pi r^2$

$A=\pi (4)^2$

$A=\pi*16$

$A=16\pi$

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Question

What is the area of a circle with diameter of ?

Tap to reveal answer

Answer

The formula for the area of a circle is $A=\pi r^2$ .

The problem gives us the diameter, however, and not the radius. Since the diameter is twice the radius (), if the diameter is , the radius will be .

Plug this value into our given equation:

$A=\pi r^2$

$A=\pi (8)^2$

$A=\pi*64$

$A=64\pi$

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