Cost, a price, profit

Three numbers. Profit is not a feeling.

Cost is what goods cost before you sold them (lemons, sugar, cups, maybe a fee a teacher says). A price is what you ask. Profit is a price minus cost per piece, times a count, minus further costs. A table may add up. The mark is a price decision, not SUM.

Jakub: a price 20, “we take a lot”. Cost 18. Profit 2. 10 cups = 20. Less than juice. Tereza: cost 8, a price 20, profit 12. An honest unit. Jakub wanted cheap like a trap. Tereza wants profit that can carry a team, not a pyramid.

A minus may be

When cost 12, a price 10, profit −2. That is a discount under cost. Shopper would say a lie, or a gift. Till boss: either a gift (a rule), or a mistake. Not “free with postage” in a costume.

Inflation: lemons get more expensive. Recalculate cost. Planner.

Do not compare profit with a classmate’s pocket money. A ranking of companies in year five is poison.

Tereza wants to shorten it to “it will be fine somehow”. Jakub asks what the lesson Cost, a price, profit is for, when a table can do a sum. A sum does not count respect, a PIN, a trap or an envelope. The core is: Profit = a price − cost. A minus is data, not shame. A feeling is not a number.

Adults pay the rent. The card, the account and the PIN belong to a parent. A child’s email does not belong here. Pocket-money numbers do not belong on the network. If you break these rules in the lesson “Cost, a price, profit”, you know a word, not the course.

A cup cost 8, a price 20, profit 12. 15 pcs = 180 profit, if everything sells. When 5, profit 60. A count is a sale calendar. Until “when it does not sell”.

Practice numbers, not a bank statement. Tereza has 80 Kč in the want envelope. Jakub pushes a step this lesson can name. When Tereza uses the core, either it waits for a parent, or it fits the envelope. If not, anger and a hole are left — proof of pressure, not that the lesson is pointless.

Why this right now

You are in the course Money with Martin, level Till boss. You can write numbers in a notebook or a table, but the topic is money and decisions, not Excel formulas. The account, the card and the PIN belong to a parent. A child’s email does not belong here. Do not put pocket-money numbers on the network.

This is not the Sheets with Martin course. A table may help, but the mark of success is a decision, not SUM.

You will know this lesson by one sentence: Profit = a price − cost. A minus is data, not shame. A feeling is not a number. When you can say it to a parent or a teacher, you have the core. The rest is practice, not magic.

Stall rules need three numbers to exist. With no them rules handle mood.

If you skip this, the next lesson in level Till boss will stand on fog. You can do 8, 20, 12 and ×10. A minus has a name. A ranking of profits no. It is not a test for marks. It is a safety net, so “Cost, a price, profit” is not only a heading.

Four things you will build from the 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.

Workshop: 8, 20, 12

Count per piece and for 10 pieces. For practice.

1. Cost 8, a price 20, profit 12. ×10.

2. A variant cost 18, a price 20. Profit?

3. A minus −2: a gift, or a mistake? Write.

4. No IČO in a notebook.

You count with three numbers per piece. SUM with no piece is Vojta’s Excel. A piece is truth.

Pocket money: Pocket money: an analogy spending/balance, but here a company. Do not write someone else’s amount, a PIN, an IBAN or “how much a classmate gets” next to it. A rule and a practice number are enough — or an honest zero.

Class trip: A trip: ticket cost ≠ profit. Do not write someone else’s amount, a PIN, an IBAN or “how much a classmate gets” next to it. A rule and a practice number are enough — or an honest zero.

Game shop: A game: a gem has no lemon cost. Do not sell. Do not write someone else’s amount, a PIN, an IBAN or “how much a classmate gets” next to it. A rule and a practice number are enough — or an honest zero.

Stall: A stall: these three numbers are the heart. Do not write someone else’s amount, a PIN, an IBAN or “how much a classmate gets” next to it. A rule and a practice number are enough — or an honest zero.

What to tell a parent with no wage and no account number: “Today I went through cost, a price, profit — Profit = a price − cost. A minus is data, not shame. A feeling is not a number.” If they have no time, a slip in the notebook is enough. Stories and class chat are not enough.

I can do three numbers per piece. If you cannot see this, let the next lesson wait. It is not shame. It is a hole in the chapter, not in you.

I name a minus. If you cannot see this, let the next lesson wait. It is not shame. It is a hole in the chapter, not in you.

SUM with no piece does not crawl in as a mark. If you cannot see this, let the next lesson wait. It is not shame. It is a hole in the chapter, not in you.

Practice: how much profit?

Count.

1. 8 and 20 per piece. Profit? ×10?

2. 12 and 10. Profit? What does it mean?

3. Why hiding cost is a lie?

4. Why profit is not Jakub’s pocket money?

Now you 💪

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

1. I can do three numbers per piece.
2. I name a minus.
3. SUM with no piece does not crawl in as a mark.

If something is missing, go back to the steps above. It is not a test for marks. It is a safety net, so you go on with certainty, not with a mess.

What to take from this lesson

• Per piece first.
• Profit is not a feeling.
• A minus = a gift or a mistake.
• Inflation reaches into cost.
• 名前s in the examples (Tereza, Jakub) 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.

© 2026 Ing. Martin Polak / AlgoRhino · コンテンツ利用規約