Rules: they are not allowed to make copies of the worksheet.  Their only materials are any color of cellophane sheets and any color of markers.  They can write only directly on the paper. The way they do it should be in the spirit of the 2-person example described below.

2-person Example: we have figured out how two people can use the same worksheet without seeing each other’s answers.

The way we did that was that the first person would use a red marker and write his answers and leave.  And the second person, when he came to do the problem, would put a piece of red cellophane in front of his eyes, making the paper look red, so that the red marker would not show up against the red paper.  And then the second person would use either a blue or a green marker to write his answer without copying the first person’s answer.  The second person can see his own writing through the red cellophane because red cellophane cannot turn blue or green to red.

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This is an original problem by me, Alex, when I was 8.  (I wanted my dad to solve a worksheet without looking at my answers.  He came up with using cellophane.  Then, I came up with the 3-person problem.)

I will post a more detailed explanation of the 2-person example soon.  I will present my solution to the 3-person problem in person on Friday, Nov. 16, 2012, at Presentation Day.  Afterward, I will post my solution on this site.