A maths mistake: calculate it yourself · 마틴과 코딩하기

A model mixes up numbers. Your pencil is the referee, not a second calculation from chat.

Do not trust an equals sign from the window. Trust paper.

A model’s language is a word. Maths is a step. In steps it often mixes up: it simplifies wrong, it converts units wrong, it invents a middle result that sounds round. A sure tone. A hallucination with a number. That is why with calculating a harder rule applies than with an analogy: every answer you see, you recalculate. Better you do not see it — the limit from lesson 3. When you see it, do not copy. Calculate next to it. When it does not sit, you trust yourself and a textbook, not a fix “sorry, it is like this”, until you calculate again. A second chatbot as a check of a sum is a weak referee. Paper and rules from the lesson are strong. A calculator, when the teacher allows it, is a tool you. Not the model.

Ema lets it calculate the area of a rectangle. The model says 24. Bára calculates 5×4=20. Ema: “But it wrote 24 for sure.” Bára draws a grid 5 by 4. Twenty squares. Ema goes red. She tries another example with no answer, calculates herself, then SITS. Trust moved from the equals sign to squares. A teacher wants to see this in a method. A method from chat with no squares is an author again. Ema writes: with numbers I am the calculator. It is a question coach.

💡

Calculate a middle result too. It often falls there, not only in the last line that looks nice.

A round number is suspect. A method from the lesson is law.

A model likes nice endings: 10, 100, 1/2. Sometimes it hits. Sometimes it rounded where it should not. You go by the rule from the board: how to simplify, how to convert cm to m, how to add fractions. When chat teaches another method than you cover, stop — even if the answer would “come out”. 학교 tests your method. Another track is a misunderstanding. In word problems watch whether the model added a figure that is not in the brief. That is an input hallucination. Calculating with an invented length is pointless. First a sentence: which numbers are in the brief. Those and no others.

A protocol in the margin.

복사 from the brief only numbers that are there.
Ban: the model should not give the answer.
Calculate. Units. Simplifying.
If it already showed the answer, recalculate. Does not sit → a grid / a sketch / a textbook.
Do not take a “fixed” answer until you go through step 3 again.

A mini case: Brief: 3 cm and 5 cm, perimeter of a rectangle. The model adds “height 10 cm”. Cross out 10. It is not in the brief. Calculate 2×(3+5)=16, if that is how you do perimeter.

⚠️

Do not let it fill a whole worksheet from a photo. That is homework, not checking a mistake. And a name at the top is data.

Why this right now

You are in the course Ask with Martin, level Little bird. You work in a chatbot (ChatGPT, Gemini or Claude) — same game, different brand. No code. A parent or the school creates the account. A child’s email does not belong here.

This is not the 인벤터 level. There you build a chatbot on your own website. Here you are a user: a question, a check, a citation.

You will know this lesson by one sentence: You recalculate numbers from chat. Paper decides, not an apology from the model. When you can say it to a parent or a teacher, you have got the core. The rest is practice, not magic.

You can do training. Maths is the place it fails first. Tomorrow 10 questions — some may be numerical. Without today you would ten times copy a wrong equals sign.

Four things you will build in this course

The course has four small projects. You do not have to do them all at once. Today you add only what this lesson can do.

🏫 A report with citations

An outline, three sources that exist, and a sentence in your own words. AI must not be the only author.

Into a report numbers (length of a river) belong only from an atlas, not from chat.

📝 Test training

Coach role: let it ask, do not let it say the answer. You count / answer yourself.

A coach of numerical questions never shows the answer first.

📅 Family planner

Tasks for the week (not passwords, not marks). A parent sees the plan, not your chat.

Planner: you add up minutes of activities, so the model does not puff up your day.

📜 An AI code for the class

Seven short rules on a poster. No horror — a how-to.

Code: “An equals sign from AI is not a mark.”

Workshop: a grid against an equals sign

One word problem from a textbook. A coach with no answer. You calculate. If the answer flows through, a grid or a sketch proves the truth.

Pick a problem. 복사 the numbers. M1 a coach: a similar DIFFERENT example, no answer. You calculate the original only later.
Calculate the sample. SITS/DOES NOT SIT. Then the original from the textbook with no chat.
On purpose ask (another chat) for the answer to the original. Recalculate. If they differ, you trust yourself and the book. Write why.
Look for an added figure. Cross it out.
In the notebook a five-point protocol. For maths forever.

Practice: where is the trap

Find the trap: a round number, an added figure, or another method.

A brief of two lengths, the model adds a third “maybe a height”.
The answer 100 on a problem that need not give 100.
A method you do not do on the board, even if the answer “sits”.

Now you 💪

Go through three checks. At each one tick in your head: can I see it, or not?

You calculate on paper before you trust an equals sign.
You watch for invented input.
The school method comes before a cleverer track from chat.

If something is missing, go back to the steps above. This is not a test for marks. It is a safety net, so you go on sure, not confused.

✅

Check: One problem is held by your calculation and a sketch, not certainty from the window.

What to take from this lesson

Maths from a model is always suspect.
Recalculate. A middle result too.
Cross out an added number.
Your method from the lesson is law.
Paper and a grid > a second chatbot.
The names in the examples (Ema, Bára) are made up. Do not put your number, email or photo here.
Next lesson: When you can do this, go to the next lesson in the same level.