This week two of the math questions were wrong. Ons was "Sreejato's ordered pairs", the other one was "Strings with brackets". Sreejato's problem as it was first posed was simply impossible (the assumption f(n)=12 was impossible, it always had to be odd). And yet there were 60 people orso that had solved the problem...by guessing the correct question! Two days later the question changed to f(n)=13. The second question was actually possible as it was first posed, but then it said my answer was wrong. Then again I saw this question change (even twice) during the week. I don't think the idea of the site is for people to guess correct questions. It would be sad if people get annoyed and started dropping out.