What is the radius of the circle?

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The ratio of the number of linear units in the circumference of a circle to the number of square units in the area of that circle is 2:5.

What is the radius of the circle?

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Answer: 5

Explanation:

The circumference of a circle = 2πr and the area of a circle = πr 2 . If the ratio of the number of linear units in the circumference to the number of square units in the area is 2:5, then five times the circumference is equal to twice the area:

5 × 2πr = 2(πr) 2

10πr = 2πr 2

10r = 2r 2

5r = r 2

r = 5

The radius of the circle is equal to 5.