Boy I'm think, I almost didn't get that one at first...A man had two horses, but he couldn't figure out which one was which. He called his friend who told him to mark one with chalk. It rained and the chalk washed off. Then, his friend told him to cut one of the horse's hair. It grew back later. Then, his friend told him to measure the two horses. The man called his friend back and tells him, "You're a genius! My grey horse is taller than my brown horse!"