Math Is Fun Forum

I found this problem and I couldn't get the ideea... I thought that the minimum number of questions is 15... but what do you think?

Ten teachers are assigned to evaluate a multiple choice test. In order to secure the privacy of the examination, each teacher was given only the answers of some of the questions. The point is to guarentee the gathering of at least five teachers for getting answers to all of the questions. (That is to say, no combination of four or less teachers will be able to collect all the answers, whereas any combination of five or more teachers will be able to collect them all).

What is the minimum possible number of questions in this test and at least how many answers should be given to each teacher?

This is a interesting problem...
This is a battlefield where X1 is lieutenant, X2 and O are captains, X3 is major, the forth line reprezents the colonels, X4 and X5 are generals.
Each of them can move on this disgram only horizontal or vertical (not on diagonal). Each of them cam reach out any other box if he jumps over a sequence of next pieces, vertical or horizontal. If one on them moves horizontal, he keeps his grade, if he moves vertical, he can loose a grade, or he cam win a grade.
For example, X1 can be major if he jumps over X2; then X2 can jump over X1, becoming colonel; X5 can jump over X2 and X1, becoming captain.
Find a sequence of moves so that O become a general (he have to hit line 5)!

Hy, I'm new here... I have to create a 6x6 magic square (sum of rows, colums, diagonals is the same). I have to use 1-once, 2-twice, 3-three times, 4-four times, 5 for five times and so on ... and 8 for eight times. I've tried many, many classic methods, but nothing worked... Any ideas, please? Thankyou!