HMMT 二月 2001 · GEN1 赛 · 第 1 题
HMMT February 2001 — GEN1 Round — Problem 1
题目详情
- What is the last digit of 17 + 5? 2 2
解析
- What is the last digit of 17 + 5? 2 3 4 5 Solution: Let 〈 N 〉 be the last digit of N . 〈 17 〉 = 9, 〈 17 〉 = 3, 〈 17 〉 = 1, and 〈 17 〉 = 7. 〈 〉 4 N 2 · 25 Since this pattern keeps on repeating itself, 17 = 1 for any integer N . Thus 〈 17 〉 = 100 103 103 〈 17 〉 = 1, so 〈 17 〉 = 3, and 〈 17 + 5 〉 = 〈 3 + 5 〉 = 8 . 2 2