if the area of a circle is 100 pi square feet , find its circumference .
"the area is given by pi * r * r . hence pi * r * r = 100 pi r * r = 100 ; hence r = 10 feet the circumference is given by 2 * pi * r = 2 * pi * 10 = 20 pi feet correct answer b"
circumface(sqrt(100))