He who knows useful things not many things，is wise.
A Problem in Arithmetic
Bill is a good student and an intelligent boy. He likes to study arithmeticarithmetic n.算术， 算法， and he can do all of the arithmetic problems in his book easily.
One day on his way to school Bill passed a fruit store. There was a sign in the window which said， “AppleSix for five cents.” An idea came to Bill and he went into the store.
聪明人不是懂得多，而是懂得有用的东西。
一个数学问题
比尔是一个好学生，也是个聪明的孩子。他喜欢学数学，课本上所有的数学问题他都能不费劲地解答。
有一天，在上学路上，比尔经过一家水果店。该店窗户上有个招牌上写着：“苹果——5美分6个。”比尔脑筋一转，进了店门。
“How much are the apples？” he asked the store.
“Six for five cents.”
“But I dont want six apples.”
“How many apples do you want？”
“It is not a question of how many apples I want. It is a problem in arithmetic.”
“What do you mean by a problem in arithmetic？”asked the man.
“Well， if six apples are wroth five cents， then five apples are worth four cents， four apples are worth three cents， three apples are worth rwo cents， two apples are worth one cent and one apple is worth nothing. I only want one apple， and if one apple is worth nothing then it is not necessary for me to pay you.”
Bill picked out a good apple， began to eat it， and walked happily out of the store. The man looked at the young boy with such surprise that he could not say a word.
“苹果怎么卖？”
“5美分6个。”
“但我不想要6个。”
“你想要几个？”
“这不是我想要几个的问题。这是个数学问题。”
“数学问题？你说这话是什么意思？”
“你看，如果6个苹果5美分，那么5个苹果4美分，4个苹果3美分，3个苹果2美分，2个苹果1美分，1个苹果就不要钱。我只要1个苹果，如果1个苹果1分钱也不要的话，那我也就没必要给你钱了。”
比尔拣了一个好苹果，开始吃了起来，然后兴高采烈地迈出了店门。那个售货员吃惊地望着这个小男孩，一句话也说不出来。