How many square inches in a 20 inch Dia. circle?

15.707963267948965 square inches. I think.

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That is a very accurate but very wrong answer.

The correct answer is 314.159 sq inches (to 3 dp).

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Yes, the correct answer is 314.159. Here's why:

• The area of a circle can be found by multiplying pi (3.14159...) by the square of the radius. (The radius of a circle is 1/2 the diameter)
• This 20" circle has a radius of 10", so its area is 3.14*10"*10"=314.159