There's nothing wrong with guessing an answer. What's horrifying is that the students actually try to solve it mathematically rather than just making up a guess

There's nothing wrong with guessing an answer. What's horrifying is that the students actually try to solve it mathematically rather than just making up a guess. And they stick with it even if the results are unreasonable (one student guessed 625, for instance.) According to the article the students didn't even try ask the teacher if the question was misprinted or something.