# TACHS Math : Area of a circle

## Example Questions

### Example Question #1 : Area Of A Circle

Find the area of a circle with the following radius:

Possible Answers:

Correct answer:

Explanation:

The area of a circle can be calculated using the following formula:

In this formula the radius is denoted by the variable, .

Substitute in the known variables and solve for the circle's area.

### Example Question #32 : Math

Which is equal to the radius of a circle with area

Possible Answers:

Correct answer:

Explanation:

The formula for the area  of a circle, given its radius , is . Replace with :

To find the radius , first, divide both sides by :

Now, find the square root of both sides. Since , 20 is the square root of 400, so

.

The radius of the given circle is 20.

### Example Question #1 : Area Of A Circle

To determine whether a machine on an assembly line is filling bottles with the correct amount of soda, twenty bottles are selected. The tenth bottle and every tenth bottle after that are taken off the line and examined.

This is an example of which kind of sampling?

Possible Answers:

Convenience sampling

Systematic sampling

Cluster sampling

Stratified sampling

Correct answer:

Systematic sampling

Explanation:

The sample in this scenario is selected from the population by choosing obects that occur at regular intervals. That makes this an example of systematic sampling.

### Example Question #1 : Area Of A Circle

What is the area of a circle that has a diameter of ?

Possible Answers:

Correct answer:

Explanation:

Recall how to find the area of a circle:

To find the length of the radius, divide the diameter by two.

Now, plug it into the equation for the area of a circle.