OG12 86

xingxc11

86. A number of people each wrote down one of the fi rst
30 positive integers. Were any of the integers written
down by more than one of the people?
(1) The number of people who wrote down an
integer was greater than 40.
(2) The number of people who wrote down an
integer was less than 70.
这种题目的思路是什么啊？望各位指教

yoonbong0908

读懂题目就好了，不需要什么思路。题目说1-30，有一定数目的学生去写，而且每个人只能写一个，那么1-30不就需要30个学生吗？正好没人写下一个数字。但是，题目问的是，1-30的数字中会不会写上一次以上。。。意思是说，>30个人，不就肯定1-30的数字里多写一次的数字存在吗？
题目理解的情况下，看条件1，40人以上，那不用说了，肯定满足！看条件2，小于70，那么可以是>30或者<30，所以不满足！