5th grader math rocks! problem - r u smarter than a 5th grader?

來源: 2010-02-08 21:28:11 [博客] [舊帖] [給我悄悄話] 本文已被閱讀:

Prove that the number 3 + 3x3 + 3x3x3 + 3x3x3x3 + .... + 3 to the power of 60 is divisible by 2x2x2x3x5x11x11x13
Hints: 1+3+3x3 = 13; 1+3+3x3+3x3x3 = 40; 1+3+3x3+3x3x3+3x3x3x3 = 121