I actually received this from my daughter who is a 4th grade teacher. It came with an attached excel spreadsheet...which was locked and only could be opened if you typed in the correct answer. Once it opened you were to put your name on the list of solvers and forward it on...didn't know of a way to attach something like that so just put the riddle in.
I've had one fellow I sent it on to who has sent me a mail every half hour because he can't solve it. I am normally "math challenged", this is why my daughter sent it to me. But I fooled her and solved it!