Agreed. IMO the second example doesn't fit within the constraints the teacher set out, so they technically failed. Someone had to buy the air pump, or borrow one from someone who bought one. It didn't just come out of thin air. I guess maybe if they 'rented' the air pump for $5 it would pass.
The third one is genius though. It brings back memories... actually, it reminds me of the time I had to a sociology presentation in high school, where my thesis was that people would believe statistics without question. Of course, all my data to arrive at this conclusion was made up which I then told the class at the end - some sort of gotcha moment. In order to make it look like I actually did to work though, I presented even more survey results and statistics, but those were also made up - I just didn't tell them that. God damn, I was a lazy kid.