HMMT 十一月 2008 · GEN1 赛 · 第 2 题

英文解析

2. [ 3 ] What is the units digit of 7 ?
   1 2 3 4 5 6
   Answer: 7 Note that the units digits of 7 , 7 , 7 , 7 , 7 , 7 , . . . follows the pattern 7 , 9 , 3 , 1 , 7 , 9 , 3 , 1 , . . . .
   The 2009 th term in this sequence should be 7.
   4 4 502
   Alternate method: Note that the units digit of 7 is equal to 1, so the units digit of (7 ) is also
   4 502 2008 2008 2009