Well, if you can't grasp this sort of questions at all, just try simpler cases, like 3 digit numbers with only using 3 digits.

[What are the options? I read it as you HAVE to use all the digits. So our options are: 123 and 132, 213, 231, 312, 321, indeed we have (3*2*1)=6 options. ]Because we have only 3 different starting numbers, pulling out 4 sheets will ensure we'll get two sheets with the same starting number.

I think you can solve the question now.

Btw everything between "[" and "]" isn't even needed. :P