Am I dumb?

I was directed to this quiz. I managed 25/25. So I thought I would try the impossible quiz. That is, it is impossible to get 100% (first time). It was significantly harder, I only got 15/20. They also have an IQ test, though I am not certain how accurate these internet tests are; I mean 20 questions seems a little too few. I have never done a real IQ test, it is not something that was done at school. Though I believe these tests may be a little more common in the United States.

I guess the ratings for the first 2 are skewed to the right as some people are likely to redo the quiz after they find the answers.