SAT Math : How to find the length of the diameter

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #11 : How To Find The Length Of The Diameter

The area of a circle is . Find the diameter. 

Possible Answers:

Correct answer:

Explanation:

The formula for the area of a circle is

with r being the length of the radius.

Since we know that the area of the circle is

we can solve for r and get 12. (Do so by canceling out the two pi's and taking the square root of 144). Once we know the radius, we can easily find the diameter, since the diameter is twice the length of the radius. Therefore, the diameter is 24, as

Example Question #11 : How To Find The Length Of The Diameter

Give the diameter of a circle with radius forty-two inches.

Possible Answers:

None of these

Correct answer:

Explanation:

The diameter of a circle is twice its radius, so if a circle has radius 42 inches, its diameter is 

 

Divide by 12 to convert to feet:

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