Question

What is the diameter of a circle that has an area of 452.16 mm 2?

Answer 1

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Given Area, find radius 
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Area = πr²

πr² = 452.16 mm²

r² = 452.16 ÷ π

r² = 143.93 mm

r = √143.93

r = 12mm

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Radius Found, Find Diameter
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D = r x 2 

D = 12 x 2 = 24 mm

Answer 2

Diameter= square root of (452.16/pi)*2 =23.99391574 or you can round top 24 mm. 
hope i helped