by Bill Graham

I was at a math conference in Palm Springs a few years ago (I know it’s a tough life, but somebody has to go to these things). One of the speakers challenged us to arrange the four digits 4, 4, 7, and 7 to equal 24 using only +, -, x and ÷. She said it was really tough. You can’t use a square root.

I worked on this problem off and on for two days and became convinced that either it was impossible or I had misunderstood it. Finally, on the way home from the conference late Saturday evening, while my wife was nodding off beside me as she usually does on car trips, the light bulbs started to go on in my brain. I solved the problem while driving down Interstate 10 with only minor swerving and one missed off ramp. I was, and am very proud of myself. I promise you, there’s no trickery.