Pre-Algebra : Area

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

Example Question #161 : Area

Find the area of a circle with a radius of .

Possible Answers:

Correct answer:

Explanation:

Write the formula for area of a circle.

Substitute the radius.

Example Question #162 : Area

Find the area of a circle with the diameter of .

Possible Answers:

Correct answer:

Explanation:

Write the formula to find the area of a circle.

The radius is half the diameter.

Substitute the radius into the formula.

Example Question #46 : Area Of A Circle

The diameter of a circle is 21.  Which of the following is the closest area?

Possible Answers:

Correct answer:

Explanation:

Divide the diameter by two to obtain the radius.

Write the area of a circle.

Substitute the radius and solve.  Assume .

The rounded answer is .

Example Question #47 : Area Of A Circle

Find the area of a circle with a circumference of .

Possible Answers:

Correct answer:

Explanation:

Write the circumference formula and substitute the circumference.

Now solve for r by dividing  on each side.

Write the formula to find the area of a circle.

Since we solved for the radius in the above calculation, we will substitute that found value into the area formula and solve.

Example Question #41 : Area Of A Circle

Find the area of a circle with a diameter of 12.

Possible Answers:

Correct answer:

Explanation:

First identify the relationship between diameter and radius of a circle. Then, divide the diameter by two to get the radius.

Write the formula for the area of a circle.

Substitute the radius.

Example Question #49 : Area Of A Circle

Find the area of a circle with a diameter of .

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

To obtain the radius, divide the diameter by 

Substitute the radius into the area.

Example Question #50 : Area Of A Circle

Find the area of a circle in  if the radius is .

Possible Answers:

Correct answer:

Explanation:

Convert  to .  There are  in a foot.

Write the formula for area of a circle and substitute the new radius.

Example Question #51 : Area Of A Circle

Determine the area of a circle with a radius of .

Possible Answers:

Correct answer:

Explanation:

Write the equation to find the area of a circle.

Substitute the radius.

Example Question #52 : Area Of A Circle

Find the area of a circle if the radius is 24.

Possible Answers:

Correct answer:

Explanation:

Write the formula for the area of a circle.

Substitute the radius.

When multiplying two digit numbers together remember to do it in steps.

First multiply , the six will stay in the ones place and the one will be carried to the tens place above the two.

      

       

Now multiply four and the two (highlighted in red above) then add the one that was carried over.

This number goes next to the six.

     

       

Placing a zero in the ones places signifies that we are in our second step of multiplication. We will multiply the two and four (highlighted in red). 

     

     

Now we will multiply two and two,

     

 

From here add down to get the final product.

Therefore the final area is,

.

Example Question #53 : Area Of A Circle

Find the area of the circle if the radius is .

Possible Answers:

Correct answer:

Explanation:

Substitute the radius into the formula for the area of a circle.

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