My geometry teacher would offer what he called IOUs to students who answered difficult questions or otherwise impressed him. After we collected enough, we could trade them in for various perks such as removing the usual penalty that came with turning in homework late.

Pretty early in the year, he offered up a flawed postulate: “Multiplying a number by another number always results in a larger number.” He offered out IOUs to anyone who could disprove him. He got all the obvious answers from various kids: zero, negative numbers, decimals, etc. After they were all used up, I decided to try a shot in the dark for a second IOU.

Me: “I’m not sure if it works, but what about imaginary numbers?”

Teacher: “How do you know about imaginary numbers?”

Me: “Our science teacher rambled a lot last year. He told us he wouldn’t have trouble giving us negative points because he learned to do far more complicated math like imaginary numbers once.”

Teacher: “Do you know what imaginary numbers are?”

Me: “Not really, but would they make a number bigger?”

Teacher: “I don’t know if they would make it bigger or not, but I’ll give you an IOU just for thinking to try imaginary numbers.”

I got my coveted IOU, but I was still disappointed. This was a math teacher. How could a math teacher not know what happened to the size of a number if you multiplied it by another number? Math teachers should understand imaginary numbers, shouldn’t they? The fact that he wasn’t able to answer what should be such a simple question frustrated me so much that I set out to find out the answer myself.

First, I asked my sister, who was two years older and had learned about imaginary numbers already, but she couldn’t answer whether multiplying by one made a number bigger. I tried my mother, an accountant and presumed master in math, and she couldn’t answer me. I didn’t try my father as I knew his skills didn’t reside in math, but a week later, when my uncle came to eat out with us, I tried him. He was a smart programmer, and programmers were supposed to know math, right? He couldn’t tell me, either.

Every single adult I tried could not answer my question. Most of them seemed to not fully remember what imaginary numbers were. With each failed answer, I grew more frustrated, but also more committed to solving this conundrum once and for all.

Eventually, I gave up on asking adults and decided to research the question online. This was back when the Internet was new and search engines were abysmal, so it wasn’t as easy a feat as it would be today. I partially taught myself what imaginary numbers were by reading an online encyclopedia about them, though I was still confused about some things, such as why everyone insisted on charting them on graphs.

Finally, I thought I might understand the problem, so I caught my geometry teacher after class to verify if I was right.

Me: “Do imaginary numbers not have a size?”

Teacher: “What do you mean?”

Me: “Like, if you have a normal number and an i-number added together, you can’t combine them to get a single size from them?”

Teacher: “Not really. You can calculate a magnitude by treating the two parts as points on a plane and using Pythagorean’s theorem, but that’s not really the same as a size.”

I had no clue what he meant about calculating magnitude, but all I cared about was that he had confirmed that complex numbers didn’t have a size.

Me: “Why didn’t you say that the first time?!”

Teacher: “First time?”

Me: “When I asked if you could multiply a number by an imaginary number to make it smaller.”

Teacher: “Oh, that. I gave you the IOU so we wouldn’t have to discuss the various ways you could handle the size of a complex number.”

Me: “But you said you didn’t know what would happen!”

Teacher: “Have you been trying to figure out if imaginary numbers made things smaller for the last month?”

Me: “No one was able to tell me what would happen.”

Teacher: “You could have just asked me.”

Me: “You said you didn’t know!”

My teacher was clearly a bit amused by my frustration but trying to keep a straight face at that point.

Teacher: “And did you learn what imaginary numbers were in that time?”

Me: “Sort of.”

Teacher: “Well, what do you know?”

Me: “The ‘i’ means the square root of negative one, which shouldn’t exist, but if you keep it around as an ‘i’, you can still solve problems with it anyway. But there was a lot of other math for using it that I didn’t understand.”

Teacher: “There is lots of math using imaginary numbers that math majors in college don’t fully understand. You still learned about imaginary and complex numbers well enough to answer your own question. If you ask me, that’s impressive enough to be worth two IOUs. But next time, just ask me after class if you want to know something like that.”

I was then sent to run off to try to make gym class in time. I was still slightly frustrated that my teacher hadn’t just told me that from the start, but I admit that managing to earn not just one but two IOUs at once seemed an impressive enough feat to mostly appease me.

A similar thing to this story happened to me in high school. It was highly annoying, and, to be honest, it still infuriates me thirty years later that anyone can be this ill-equipped for their job.

For whatever reason, my science teacher didn’t like me. Mostly, she seemed annoyed to meet me outside of school, and I get that she didn’t want to mix her work life and personal life, but it wasn’t my fault that her children’s daycare provider was my next-door neighbour. ([Teacher] lived one street over from us.) Thus, I met her or her children almost daily after school.

[Teacher] sucked at math. If we had a weekly test and I had 12 points on one page and 14 points on the other, she would add it together and conclude that my total point was 10 out of 26. It never made any sense. I would point out her error, and she’d tell me that she’d correct it in her notes and it wouldn’t affect my grade. Hah. Suuuuuuuuuure.

She never made these errors on other students’ tests, just mine. It was weird. Oh, well.

Then, we had the major exam for the semester. The day before, a Thursday, I was in massive pain and went to the school nurse, who sent me to the hospital, where I was booked for urgent surgery during said exam.

So, I went back to school to talk to [Teacher] as I had missed her class for the hospital visit.

Teacher: “Come straight after surgery to take your exam.”

I showed up on Friday, almost unconscious from the massive pain as the anesthesia from the surgery was fading off. [Teacher] just looked at me and told me:

Teacher: “Just take the exam during class on Monday.”

Me: “You could take my books to make sure I can’t study during the weekend.”

Teacher: “Go home.”

And she closed the door in my face.

[Teacher] was sick that Monday, but I still got to take the exam. And then, I fell ill and missed a couple of weeks, so when I finally was back in school, the grades were final. [Teacher] threw my exam at me. The score was mediocre, and I knew I had done better than that, so as she began berating me for my poor results, I quickly checked the test. Then, I heard her yammer about my poor results on our weekly exams. 

Darling, I have the weekly exams right here. Let’s take a look at them. Oh, yes, she hadn’t corrected her stupid errors and still had those abhorrent “results” she had somehow conjured up by failing first-grade math. And THIS exam? She had outdone herself.

As usual, she was unable to add two sums together (13 + 26 = 12), AND she had missed grading the major task, worth a whopping 25 points. I don’t remember the exact numbers, but I think her original result was that I had 21 out of 50, whilst the actual result was 49 out of 50. As I said, infuriating. She had given me a grade THREE STEPS below what I had actually achieved, and she told me that she couldn’t possibly change it nor raise it more than one step the next (and final) semester.

[Teacher]’s solution was that I was relieved from attending class. I could skip the entire semester and she would still raise my grade. She had effed up that badly. But I like school. I like to learn stuff. So, I attended class, did all the assignments, got top scores (she still never calculated the results correctly because she was a moron), and graduated with a grade two steps below what I had achieved.

Yup, I’m still pissed about that.

[Teacher] also had to start the semester by telling my extremely ambitious classmates that no one would be able to get top grades because I was the top student and I couldn’t get it, and thus, no one else could, either. They really hated me because of it — like it was my fault [Teacher] was such a moron. Oh, and she actually could raise grades more than one step as she did it for one of my classmates, so she was a LYING moron.

One of my priorities as a teacher was to make sure I NEVER missed grading anything. And that my calculations were correct. It is my duty as a teacher to ensure that the students get the grades they deserve.

There was no way for me to dispute my grade. As a teacher, I always make sure that the students know how to dispute grades, and if they want to dispute another teacher’s exam, I listen to their complaints and support them however possible. That only happened once, but it was not a pleasant battle. However, the students who asked for my assistance were students I was mentoring, so I was the obvious go-to person for help. In the case of [Teacher], this would have been an issue, because, well, [Teacher] WAS my mentor.

Related:
Even Gifted Teachers Can Make Mistakes

I was given a $100 gift certificate for a massage one year for my birthday. I chose a service that was exactly $100. As I was checking out, the girl at the counter asked me:

Cashier: “Would you like to add a gratuity?”

Me: “Yes, twenty.”

Cashier: *In a snotty tone* “Dollars or percent?”

Me: “Um, either one. They’re both the same.”

Cashier: “Um, I need you to tell me which one!”

Me: “The bill is $100; 20% is the same as $20 since the total is $100.”

She looked at me like I was a total moron, sneered, and then typed on her computer.

Her face showed utter shock when her computer screen agreed with me.

Related:
Must Be Using 1% Of Her Brain

I was at the market, and I bought four of a product that cost $7. The stall owner looked confused, so I volunteered “$28” for him. He shook his head.

Owner: “Nah, that’s not right.”

He called out to another stall owner.

Owner: “Hey, what’s four times $7?”

Owner #2: “$26, I think.”

Owner: *To me* “See, I knew you were wrong.”

Me: “Oh, boy, was I!”

I left him a $2 “tip” since I’m not a monster.

A customer makes a $5 purchase and pays with a $20 bill, so I just hand them $15 in change.

Customer: “You’re not going to type the twenty into the register?”

Me: “No, I just hit the sale button. I don’t need the register to count the change.”

Customer: “How do I know you’re not short-changing me?!”

Me: “You paid with a twenty, and the item is five.”

Customer: “So?”

Me: “Twenty minus five is fifteen.”

Customer: “But without the register, how can you know that?”

Me: “Because I did the math in my head.”

Customer: “Bulls***! No one can do math in their head!”

Me: “Would you prefer I enter your twenty into the register?”

Customer: “Yes!”

I oblige and type the twenty into the register which, of course, informs us both that the change should be fifteen. The customer looks at the fifteen on the register, at the fifteen in bills on the counter, and then at me. 

Customer: *Grabbing the change* “Lucky guess!”