The inequality isn't even necessary

To prove that 70 is the correct answer, simply work backwards. Assign 70 people all five questions, so 350 answers are occupied. Since there are 410 answers in total, 60 are left: 11 from Q1, 21 from Q2, 15 from Q3, 9 from Q4, and 4 from Q5. Then, start distributing the questions evenly. Assign the 11 Q1 answers. Then, there will be 19 people of the 30 remaining who have not answered a single question. Assign Q2. Everyone now has answered at least one question, and two have answered 2. Assign Q3. There are now 17 people who have answered 2 questions. Assign Q4. There are now 26 people who have answered 2 questions. Assign Q5. All 30 remaining people have now answered two questions, and there are no more answers left. 70 people have answered three or more questions.

所有跟帖： 

• 70 is notright,the best case : 5*70=350,411-350=61,there 30 peop -jinjing- ♀ (48 bytes) () 06/22/2010 postreply 20:19:24

• I'm careless,410 not 411,but the inequolity is good.we can very -jinjing- ♀ (0 bytes) () 06/22/2010 postreply 20:29:24

• fast to get answer.(if the anwser is less than smallest number) -jinjing- ♀ (0 bytes) () 06/22/2010 postreply 20:33:56

• 回複：I'm careless,410 not 411,but the inequolity is good.we can ve -commentate- ♂ (32 bytes) () 06/23/2010 postreply 07:11:14

• 回複：回複：I'm careless,410 not 411,but the inequolity is good.we can -jinjing- ♀ (166 bytes) () 06/23/2010 postreply 09:00:17

• 回複：回複：回複：I'm careless,410 not 411,but the inequolity is good.we -commentate- ♂ (94 bytes) () 06/24/2010 postreply 10:11:47

• 回複：回複：回複：回複：I'm careless,410 not 411,but the inequolity is good. -jinjing- ♀ (204 bytes) () 06/27/2010 postreply 14:37:06