View source for 2016 CEMC Gauss (Grade 8) Problems/Problem 10

== Problem==
The circumference of a circle is <math>100\pi \text{cm}</math>. What is the radius of the circle?

<math> \textbf{(A)}\ 20 \text {cm} \qquad\textbf{(B)}\ 100 \text {cm} \qquad\textbf{(C)}\ 50 \text {cm} \qquad\textbf{(D)}\ 25 \text {cm} \qquad\textbf{(E)}\ 10 \text {cm} </math>
== Solution==
Let <math>r</math> be the radius of the circle. Using the equation for the [[circumference]] of a [[circle]], we have:

<math>2\pi r = C = 100\pi</math>

<math>r = \frac{100\pi}{2\pi} = \boxed {\textbf {(C) } 50 \text {cm}}</math>

~anabel.disher