How much is four minus four

One day，the teacher inquired Peter:“How much is four minus four？”Peter was tongue－tired．The 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．

（译文）四减四等于几？

一天，老师问彼得：“4减4等于几？”彼得张口结舌答不上来。老师生气地说：“真笨！你想，我要是往你口袋里放四个硬币，而你的口袋上有个窟窿，硬币全漏掉了，那么，你衣袋里还剩下什么？”“窟窿。”彼得答道。