The remnants we have of dinosaurs are few and make it difficult to know what they actually looked like beyond their skeletal forms and feathery exteriors. It is a little-known fact that many wore coats in the winter, and those coats had large wooden buttons. Intelligent troodons ran a button factory in which they developed a system for cutting four holes, each with a radius of y inches, out of a circular piece of wood with a radius of x inches. (There was a steady supply of such circular pieces; it is not understood where they came from.) Assuming the troodons’ motor control was sound and the holes did not overlap, write a formula for the area of remaining wood, and evaluate the formula if x = 10 inches and y = 2 inches. (Use 3.14 for )
Solution
The area of the original plywood is . Each hole has an area ; there are four of them. Thus the remaining area is .
If and and we use , we get
Interesting extension: If you're going to cut four round buttons out of that circular piece of wood with radius 10 inches, what's the maximum radius for the buttons?