一个人有50元，买了袜子20元，剩30元，然后买了水果15元，剩15元，接着买了饼干9元，剩下6元，最后坐车6元，请问为什么所有剩下的钱加起来是51元？

为什么呢？因为把每次剩下的钱加起来，本来就是51元啊！为什么一定要是50元呢？

推荐阅读：
How to Find Common Characters in an array of Strings?　 How to Turn a Binary Search Tree into a Increasing Order Search 　 How to Free TCP/UDP Port on Windows Using netstat and taskkill?　 The Review of cozmo robot from Anki　 Scaling Digital Marketing Agencies Through White Label Solutions　 How to Solve the Lemonade Change Problem by Simulation Algorithm　 How to Sum within A Range in a Binary Search Tree?　 Magik Says Happy Valentines by Drawing a Heart to Console　 Cloud-Ready Infrastructure Optimization　 Freedom of Speech Isn’t So Free