# GED Math : Radius and Diameter

## Example Questions

### Example Question #21 : Radius And Diameter

Find the diameter if the radius is .

Explanation:

The diameter is double the radius.

Do not multiply the coefficient into the radical.

### Example Question #22 : Radius And Diameter

Determine the diameter if the radius is .

Explanation:

The diameter is double the radius.

Substitute the radius into the formula.

### Example Question #23 : Radius And Diameter

A circle is circumscribed in a square as shown by the figure below.

If the area of the square is , what is the area of the circle in square inches? Use .

Explanation:

Start by finding the length of a side of the square from the area.

Plug in the area to find the length of the side.

Now, notice that the diameter of the circle is the same as the length of a side of the square.

Thus, the diameter of the circle is , which means the radius is . Recall how to find the area of a circle:

### Example Question #24 : Radius And Diameter

Determine the diameter with a radius of .

Explanation:

The diameter is double the radius.

### Example Question #25 : Radius And Diameter

Determine the radius if the diameter of a circle is:

Explanation:

The radius is half the diameter.

Multiply the diameter by one-half.

### Example Question #21 : 2 Dimensional Geometry

Determine the radius of the circle with a diameter of .

Explanation:

The radius is half the diameter.  Multiply the given diameter by half.

### Example Question #27 : Radius And Diameter

You have a giant gong that has a diameter of . Find the radius of the gong.

Explanation:

You have a giant gong that has a diameter of . Find the radius of the gong.

To relate radius and diameter, use the following formula:

So, to find our radius from our diameter, divide by 2:

### Example Question #28 : Radius And Diameter

While doing your homework, you become distracted by the 3 holes on the margin of your paper. You estimate that the holes have a diameter of 2.5 cm. What is the radius of the circles?

Explanation:

While doing your homework, you become distracted by the 3 holes on the margin of your paper. You estimate that the holes have a diameter of 2.5 cm. What is the radius of the circles?

Recall that your radius is always exactly half of the diameter. A diameter spans the entire width of a circle, while a radius goes from the center to the edge.

So, to find our radius, divide our diameter by 2

### Example Question #29 : Radius And Diameter

What is the radius of a circle if it has a circumference of ?

Explanation:

In order to solve this problem, it's important to understand the relationship between the two terms mentioned: radius and circumference.

The circumference of a circle can be solved for with the formula: , where r is radius. By substituting the circumference value into the equation, we should be able to solve for the radius fairly quickly.

Therefore, the radius of the circle is

### Example Question #30 : Radius And Diameter

If a circle has a circumference of , what is its radius?