Radius and Diameter - GED Math

Card 1 of 200

0

Didn't Know

0

Didn't Know

Knew It

0

1 of 2019 left

Question

What is the diameter of a circle with a radius of 9?

Tap to reveal answer

Answer

The diameter of a circle is twice the radius:

Plug in the radius value:

← Didn't Know|Knew It →

Question

What is the radius of a circle given the diameter is 22?

Tap to reveal answer

Answer

The radius is half of the diameter, or 11.

← Didn't Know|Knew It →

Question

What is the radius, in inches, of a circle with a diameter of 12 inches?

Tap to reveal answer

Answer

The radius is half of the diameter:

From here we plug in our diameter measure of 12 and solve for the radius:

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

← Didn't Know|Knew It →

Question

What is the diameter of a circle with radius of 10 inches?

Tap to reveal answer

Answer

The diameter is twice the radius:

← Didn't Know|Knew It →

Question

What is the radius of a circle that has a circumference of $36\pi$ ?

Tap to reveal answer

Answer

The equation for circumference of a circle is as follows:

$C=2 \pi r$

Plug in the given values and solve for the radius:

$36\pi=2\pi r$

Now we divide each side by $2\pi$ :

← Didn't Know|Knew It →

Question

Find the diameter of a circle that has a circumference of $25\pi$ ?

Tap to reveal answer

Answer

We know the equation for the circumference of a circle is $C=2\pi r$ . We also know that the the diameter is the twice the radius, so we can write $C=D\pi$ .

Plug in the given values and solve:

$25\pi=D\pi$

← Didn't Know|Knew It →

Question

What is the diameter of a circle with an area of $144\pi$ ?

Tap to reveal answer

Answer

In order to solve this question, start by finding the radius. Recall that the area of a circle is computed as:

$A=\pi $r^2$$

For our data, this is:

$144\pi = \pi $r^2$$

Solving for , we get:

or

Now, recall that the diameter is double the radius. Thus, it is .

← Didn't Know|Knew It →

Question

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

Tap to reveal answer

Answer

Recall that the circumference formula is:

$C=2\pi r$

Now, for your data, this gives you:

$17=\pi r$

You need to be careful, for some students get confused when they have to divide by $\pi$ . However, just treat it like any other number or variable. This means that you can solve for and get:

$r=\frac{17}{\pi}$$

← Didn't Know|Knew It →

Question

What is the diameter of a circle given the area of 30?

Tap to reveal answer

Answer

Write the area formula of a circle.

$A=\pi $r^2$$

Substitute the area.

$30=\pi $r^2$$

Divide by pi on both sides.

$\frac{30}{\pi}$=\frac{\pi $r^2$}{\pi}$

Square root both sides.

$r=$\sqrt{ \frac{30}{\pi}$}$

The radius is: $$\sqrt{\frac{30}{\pi}$}$

The diameter is double the radius.

The answer is: $2$\sqrt{\frac{30}{\pi}$}$

← Didn't Know|Knew It →

Question

What is the diameter of a circle if the area is $14\pi$ ?

Tap to reveal answer

Answer

Write the formula for the area of a circle.

$A=\pi $r^2$$

Substitute the area into the equation.

$14\pi=\pi $r^2$$

Divide by pi on both sides.

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

$r=$\sqrt{14}$$

The diameter is twice the radius.

The answer is: $2$\sqrt{14}$$

← Didn't Know|Knew It →

Question

If the diameter of a circle is 12 feet, what is the radius in yards?

Tap to reveal answer

Answer

There are three feet in one yard.

Using dimensional analysis, we can determine the given diameter in yards first.

$12 \textup{ ft}($\frac{1 \textup{ yd}$}{3 \textup{ ft}}) = 4 \textup{ yds}$

The radius is half the diameter.

The answer is: $2 \textup{ yds}$

← Didn't Know|Knew It →

Question

Determine the diameter if the radius is $$\frac{2}{3}$x-4$ .

Tap to reveal answer

Answer

The diameter is double the radius.

$2($\frac{2}{3}$x-4) = $\frac{4}{3}$x-8$

The answer is: $$\frac{4}{3}$x-8$

← Didn't Know|Knew It →

Question

Determine the diameter of a circle if the radius is $2$\frac{1}{3}$$ .

Tap to reveal answer

Answer

The diameter is twice the radius.

Convert the mixed fraction to an improper fraction.

$D= 2($\frac{7}{3}$) = $\frac{14}{3}$$

The answer is: $\frac{14}{3}$

← Didn't Know|Knew It →

Question

Determine the diameter if the radius is $\frac{1}{8}$ .

Tap to reveal answer

Answer

The diameter is twice the radius.

Multiply the radius by two.

$\frac{1}{8}$ (2) = $\frac{2}{8}$ = $\frac{1}{4}$

The answer is: $\frac{1}{4}$

← Didn't Know|Knew It →

Question

What is the radius if the diameter of a circle is $\frac{\sqrt3}{3}$ ?

Tap to reveal answer

Answer

The radius is half the diameter of a circle.

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

This is also similar to multiply diameter by one-half.

$$\frac{\sqrt3}{3}$ \times $\frac{1}{2}$ = $\frac{\sqrt{3}$}{6}$

The answer is: $$\frac{\sqrt{3}$}{6}$

← Didn't Know|Knew It →

Question

What is the radius with a diameter of $\frac{\sqrt3}{2}$ ?

Tap to reveal answer

Answer

The radius is half the diameter.

Multiply the diameter by one-half.

$\frac{\sqrt3}{2}$ \cdot $\frac{1}{2}$ = $\frac{\sqrt3}{4}$

The answer is: $\frac{\sqrt3}{4}$

← Didn't Know|Knew It →

Question

Find the radius of a circle with an area of $8\pi$ .

Tap to reveal answer

Answer

Write the formula for the area of a circle.

$A = \pi $r^2$$

Substitute the area.

$8\pi = \pi $r^2$$

Divide by pi on both sides.

$\frac{8\pi }{\pi}$=\frac{ \pi $r^2$}{\pi}$

Square root both sides.

$r= \sqrt8 = 2\sqrt2$

The answer is: $2\sqrt2$

← Didn't Know|Knew It →

Question

Find the value of the diameter if the radius is $5\pi-2$ .

Tap to reveal answer

Answer

The diameter is double the radius.

Multiply the quantity by two.

$2(5\pi-2) = 10\pi -4$

The answer is: $10\pi -4$

← Didn't Know|Knew It →

Question

Determine the radius if the diameter is $$\frac{\sqrt{2}$}{3}$ .

Tap to reveal answer

Answer

The radius is half the diameter.

Multiply the diameter by half.

$\frac{\sqrt{2}$}{3} \cdot$\frac{1}{2}$

The answer is: $\frac{\sqrt2}{6}$

← Didn't Know|Knew It →

Question

Determine the radius of the circle if the diameter is $\frac{3\sqrt5}{7}$ .

Tap to reveal answer

Answer

The radius is half the diameter. To find the radius, multiply the diameter by half.

$\frac{3\sqrt5}{7}$ \cdot $\frac{1}{2}$ = $\frac{3\sqrt5}{14}$

The answer is: $\frac{3\sqrt5}{14}$

← Didn't Know|Knew It →

0

Knew It