You sneaky, sneaky Quizmaster... *shakes finger* You think that trick one is funny, do ya? I'll have you know... it was! haha. It stumped me for the longest time! I kept thinking, "I don't understand... nothing goes into 17 AND 20!"
Some people really don't like trick questions. Far too much time. Please add some genuinely difficult questions on at the end, and cut the time to two minutes.