A farmer has 300m of fencing to make a pen for his chickens. The fence will form an arc against two walls at an angle of 120 degrees. What is the radius of the pen formed?
120 degrees is 1/3 of a circle. Therefore the perimeter of the fence is 1/3 of
the circumfrence (2 pi r/ 3). Set 300m = 2 pi r / 3. Solving for r gives 143m.
