THE PIGPEN PROBLEM

Venture to the barnyard for a lesson in math!

Goat, Chicken, and Sheep face an ultimatum from Farmer Ed: Build a pigpen, or forfeit their barn dance. They have 20 feet of fencing, and the pen must enclose the largest possible area. Impatient Goat plans a 20-foot perimeter but hastily hammers together a rectangle just nine feet by one, “barely big enough for a mouse.” Sheep patiently explains how to calculate the area (“Multiply the length times the width”), but again, Goat jumps into rebuilding without math. Now the pen is eight feet by two. The next rash iteration is three by seven: 21 feet in area. Better, and now Chicken notices a pattern. Sheep presses on with the explanation (“Each time we increase the length by one and decrease the width by one, the area of the rectangle increases”), only to be interrupted by Goat, who tries four by six and then nine by one again. At last Sheep draws the five-by-five plan, yielding the largest area, as all agree—even Farmer Ed, who has one more request, however: a 100-square-foot triangular pen! The final two pages explain perimeter and the area of a rectangle. The jokes are corn-fed, the math clear (though there’s no help with the triangle problem), and the goggle-eyed illustrations are wild, wacky, and amusing.

A practical and entertaining introduction to plane geometry.