### All GED Math Resources

## Example Questions

### Example Question #1 : Radius And Diameter

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

**Possible Answers:**

**Correct answer:**

The radius is half of the diameter:

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

### Example Question #2 : Radius And Diameter

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

**Possible Answers:**

**Correct answer:**

The diameter is twice the radius:

### Example Question #2 : Radius And Diameter

What is the radius of a circle that has a circumference of ?

**Possible Answers:**

4

20

18

12

**Correct answer:**

18

The equation for circumference of a circle is as follows:

Plug in the given values and solve for the radius:

Now we divide each side by :

### Example Question #4 : Radius And Diameter

Find the diameter of a circle that has a circumference of ?

**Possible Answers:**

25

12.5

20

10

**Correct answer:**

25

We know the equation for the circumference of a circle is . We also know that the the diameter is the twice the radius, so we can write .

Plug in the given values and solve:

### Example Question #5 : Radius And Diameter

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

**Possible Answers:**

6

18

16

20

**Correct answer:**

18

The diameter of a circle is twice the radius:

Plug in the radius value:

### Example Question #6 : Radius And Diameter

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

**Possible Answers:**

6

11

9

15

**Correct answer:**

11

The radius is half of the diameter, or 11.

### Example Question #3 : Geometry And Graphs

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

**Possible Answers:**

**Correct answer:**

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

For our data, this is:

Solving for , we get:

or

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

### Example Question #4 : Geometry And Graphs

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

**Possible Answers:**

Cannot be computed from the information provided

**Correct answer:**

Recall that the circumference formula is:

Now, for your data, this gives you:

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

### Example Question #3 : Radius And Diameter

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

**Possible Answers:**

**Correct answer:**

Write the area formula of a circle.

Substitute the area.

Divide by pi on both sides.

Square root both sides.

The radius is:

The diameter is double the radius.

The answer is:

### Example Question #10 : Radius And Diameter

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

**Possible Answers:**

**Correct answer:**

Write the formula for the area of a circle.

Substitute the area into the equation.

Divide by pi on both sides.

The diameter is twice the radius.

The answer is: