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

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

$30\pi$

$15\pi$

Explanation

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 $C=2(\pi)(15)$

We multiply to find the value for the circumference is $30\pi$ .

The answer is $30\pi$ .

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

$30\pi$

$15\pi$

$225\pi$

Explanation

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

$Cicumference=2(15)\pi$

We multiply to find the value for the circumference is $30\pi$ .

The answer is $30\pi$ .

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

$62\pi$

$72\pi$

$31\pi$

Explanation

To find the circumference of a circle we must first know the equation for the circumference of a circle, which is $C=2\pi r$ .

We then plug in the given value for the radius, yielding $C=2(\pi)(31)$ .

We multiply to find the value for the circumference is $62\pi$ .

Thus answer is $62\pi$ .

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

$C=32\pi$

$C=16\pi$

$C=24\pi$

$C=64\pi$

Explanation

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

$C=2(\pi)(16)$

We multiply to find the value for the circumference is

$C=32\pi$

The answer is $C=32\pi$ .

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

$26\pi$

$13\pi$

$169\pi$

$39\pi$

Explanation

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

$Circumference=2\pi\cdot Radius$

Substitute the given value for the radius into the equation:

$Circumference=2\pi\cdot13$

$Circumference=26\pi$

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

$70\pi$

$35\pi$

$1225\pi$

Explanation

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

$C=2(35)(\pi)$

We multiply to find the value for the circumference is $70\pi$ .

The answer is $70\pi$ .

What is the circumference of a circle with radius ?

$6\pi$

$3\pi$

$12\pi$

$8\pi$

$1.5\pi$

Explanation

Remember, the formula for circumference of a circle is $C=2\pi r$ .

Plug in our given values:

$C=2\pi r$

$C=2\pi*3$

$C=6\pi$

Find the circumference of a circle with a diameter of 4 meters.

$4\pi$ meters

$2 \pi$ meters

$\pi$ meters

$8 \pi$ meters

$16 \pi$ meters

Explanation

The formula for circumference is:

$C = 2\pi r$ 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:

$C = 2 \pi \cdot 2 = 4 \pi$ meters.

If the diameter of a circle is , what is the circumference?

$14\pi$

$7\pi$

$28\pi$

$49\pi$

$196\pi$

Explanation

The formula for circumference is $C=2\pi r$ . 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 :

$\frac{14}{2}=r$

Plug this value into our initial equation to solve:

$C=2\pi r$

$C=2\pi *7$

$C=14\pi$

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?

$12\pi$