The skill-testing question is actually a government requirement for any contest in Canada. It is a way of regulating contests to avoid illegal lotteries. Unlike a lottery, where winning is based on pure luck, a contest must have a "skill" component. The courts have agreed that a four-part math question can constitute a "skill", which is why you see so many contests asking you to answer a math question.
I can remember a few months ago I had a winning tab from McDonald's Monopoly game. It was for something really small (fries or a small drink...I forget which) and the girl took the tab, stuck it to a form and had me fill out the form with my name and answer to a skill-testing question.
It might seem strange that they would have you fill one out for winning points since the points themselves don't have any value. However, since it is a contest--only one winner--and the points can be redeemed for something of value, it probably still falls under this rule.
I found a great article on Canadian contest regulations:
http://contests.about.com/od/sweepst...llquestion.htm
Hope this helps!