1. Each of the students in a class writes a different 2-digit number on the whiteboard. The teacher claims that no matter what the students write, there will be at least three numbers of the whiteboard whose digits have the same sum. What is the smallest number of students in the class for the teacher to be correct and why?
2. What is the sum of the digits of all 2-digits numbers from 10 to 99 and why? The answer can't be anything above 1000.
3. We will call a number N green if 6 x N contains none of the digits 0,1,2,3 and 4. There are two digits such that every green contains at least one of them. One of these two digit is 1. What is the other and why?
2006-08-08
20:01:28
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4 answers
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asked by
Anonymous