2011 年 2月 27 日随笔档案 - xiatwhu

摘要： 215 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26. What is the sum of the digits of the number 21000? 阅读全文

posted @ 2011-02-27 21:33 xiatwhu 阅读(290) 评论(0) 推荐(0) 编辑

摘要： Starting in the top left corner of a 2×2 grid, there are 6 routes (without backtracking) to the bottom right corner. 阅读全文

posted @ 2011-02-27 21:14 xiatwhu 阅读(206) 评论(0) 推荐(0) 编辑