One day, the teacher inquired of Peter: "How much is four minus four?" Peter was teacher got angry and said: "What a fool! You see, if I put four coins in your pocket, but there is a hole in your pocket and all of them leak out, now what is left in your pocket?""The hole," replied Peter。
一天，老師問彼得：“4減4等於幾?”彼得張口結舌答不上來。老師生氣地說：“真笨!你想，我要是往你口袋裏放四個硬幣，而你的口袋上有個窟窿，硬幣全漏掉了，那麼，你衣袋裏還剩下什麼?”“窟窿，”彼得答道。