Education: Q.E.D.

The entire geometry class of the Westlake School for Girls in Los Angeles was agreed. Not one of them could make head or tail of the problem: “The common external tangent of two tangent circles of radii 8 inches and 2 inches is — .” Fortunately, the class secretary, 15-year-old Johanna Mankiewicz, had an inspiration. All the class had to do, she decided, was to write a letter to the Most Famous Physicist in the World.

“I realize,” Johanna wrote, “that you are a very busy man, but you are the only person we know of who could supply us with the answer . . .” Then, after relaying the problem, she commented: “I think you will agree it is the hardest thing!”

Apparently, it wasn’t too hard for the Famous Physicist, for he replied by return airmail, though he forgot to put a 6¢ stamp on the envelope. In any case, Johanna got his letter, with a diagram* and instructions on how to do the problem. The Physicist’s diagram merely suggested that a right triangle can be formed from 1) the line of centers, 2) a line parallel to the common tangent and running through the center of the smaller circle, and 3) the radius of the larger circle. The length of the tangent can then be found by applying the Pythagorean Theorem. “This,” concluded the great man, “gives the solution.” Then he signed his initials—A.E., for Albert Einstein.

*Probably a rather baffling diagram for Johanna. Instead of drawing the tangent circles the problem called for, the Physicist spread his circles apart, introduced a third circle with a radius equal to the difference between the radii of the original two.