Question

What is:
Area of a circle with 10cm diameter?
Perimeter of a semicircle with radius 14cm?
The radius of a circle whose circumference is 80cm?

Answer 1

area of i circle: 25*Pi
perimeter: (2*Pi*14)/2=14Pi
radius: 2Pi*r=80
r=80/2Pi
r=40Pi

Answer 2

Area of a circle is given by \(\pi r^{2}\), or \(\frac{1}{2}\tau \: r^{2}\) = \(78.5 cm^{2}\)
Perimeter of a circle is given by \(2 \pi r\) or \(\tau \: r\) = \(44.0 cm\)
Radius is given by \(\frac{c}{2\pi}\) or \(\frac{c}{\tau}\) = \(12.7cm\)