Area of a Circle Practice

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Question 2

Given a circle with the area of 314in2. Find the radius of the circle. Take π as 3.14.


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Select and check your answer...

A. 8 in2
B. 8 in
C. 10 in2
D. 10 in

Step by Step Solution

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    Step 1

    The picture below shows the circle with the radius r.

    a circle with the radius r
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    Step 2

    To find the radius of a circle, we can start with the formula for the area of a circle:

    formula for the area of a circle
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    Step 3

    Since the value of the area is given as 314 in2, we can substitute A with 314. Similarly, we can substitute π with 3.14. These are shown below:

    calculating the radius of a circle
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    Step 4

    Now, we have 3.14r2 = 314. To get closer in finding r, we need to remove 3.14. To do so, we divide both sides of the equation with 3.14 as shown below:

    dividing both sides with 3.14
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    Step 5

    Now, we have r2 = 100. Since r square is a multiplication of r two times, we can find r by taking the square root of 100. This is shown below:

    square root of 100 is 10
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    Step 6

    Now, the calculated number 10, has no meaning unless we include the unit for it. Since the area is in in2, r will be in inch. Hence:

    r = 10 in