Mickey7Kid gave a reasonable answer without all the math bullshit
KaryoplasmaWhen I was in elementary, my teacher said that “Lutetia” was how the Romans called the city of Liege. As an avid reader of Asterix comics, I knew this isn’t true and corrected her and said it was the Roman name of Paris. She insisted that it is Liege. Anyway, the next day, she came back to class and said that she looked it up and that I was indeed correct and Lutetia referred to Paris and gave me a chocolate bar.
In my country, the written final exams include a Q&A section in the beginning of the test, where the teacher and the headmaster are present, and where they present the tasks and students are allowed to ask questions. After that section, the headmaster leaves and students and teachers aren’t allowed to talk for the rest of the test.
I noticed a missing specification in one of the tasks. It was a 3D geometry task, and it was missing one angle, thus allowing for infinite correct results. During the Q&A section I asked about that, and my teacher looked sternly past me to the end of the room and said “I am sure the specifications are correct”. If there was an actual error in the specifications, the whole test would have been voided and would have to be repeated at a later date, for all the students attending.
As soon as the headmaster was out of the room, he came to me and asked where he made the mistake. He then wrote a fitting spec on the whiteboard.
I liked that guy. He was a good teacher.