Quandaries and Queries
Using the same notation as Penny's answer to Kay,
Substituting y from the first equation into the first and simplifying gives
which is 3.314 inches, or twice the length of the sides of Kay's window. Changing to more standard measurements this is 3 feet 3 and 3/4 inches.
Now I am going to ask you what Penny asked Kay. When you have built the playhouse send us a photograph. We often get askwd "When will I ever use Pythagora's Theorem?" and this gives a nice reply.