by Bill Graham

Farmer Humphrey has his old horse Dobbin, out in his verdant pasture, tied to a metal post with a 25-yard rope. Dobbin can munch on all the grass in a circle with a 25-yard radius.

But Farmer Humphrey wants to diversify and start raising chickens. He decides to build a chicken coop in the pasture. He figures than he can save a little money if he uses the metal post for one of the corners of the chicken coop. The dimensions of the chicken coop are 20 yards by 10 yards. Here's a diagram of the chicken coop. Obviously Dobbin is upset because the chicken coop takes up part of his former grazing space. Question: In what fractional part of the original circular area can Dobbin still graze?