A reserve

A reserve does not concern a discount

A reserve is a line that must stay until a problem happens. A delay, a broken bottle, another bus, a higher price at the till than paper expected. It is not a fourth want envelope. Do not reach into a reserve for 50% off a magnet.

Who spends a reserve because “the trip is going well” stays with no plan B. Plan B will come. Today: do not reach.

Matyáš: a reserve 40, a magnet −50% for 40. “I won.” The bus goes an hour later, a machine 35, thirst. Sofie has 40. Matyáš has a magnet and anger. The discount ate a problem that had not come yet.

A problem, not an opportunity

A discount is an opportunity of a mood. A reserve is insurance of a small trip. Mixing them is like paying insurance with a skin.

How much: for practice 10–20% of the ceiling, or a fixed 40, as a teacher says. You do not order it. You watch it on paper.

After the trip: leftover reserve has a rule (return to parents, leave in the till, split). With no rule a fight starts, who deserves a magnet backwards.

Pocket money: a mini reserve of the week (10 Kč) for a copy. The same spirit. Not for a loot box.

Sofie wants to shorten it to “it will be fine somehow”. Matyáš asks what the lesson A reserve 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: A reserve is for a problem. A discount is not a problem.

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 “A reserve”, you know a word, not the course.

A ceiling 270, a reserve 40. Remaining lines 230. Sofie holds it. Matyáš 230+40 on lines, a reserve 0. Paper lies with the name “reserve” when it is 0.

A problem: entry 170 instead of 150. Reserve −20. 20 left. It holds. With no reserve they would take food. Food is M. Wrong.

Practice numbers, not a bank statement. Sofie has 80 Kč in the want envelope. Matyáš pushes a step this lesson can name. When Sofie 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 Planner. 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: A reserve is for a problem. A discount is not a problem. When you can say it to a parent or a teacher, you have the core. The rest is practice, not magic.

A calendar and “when it runs out” need the reserve still to exist. An empty reserve is a plan that already died.

If you skip this, the next lesson in level Planner will stand on fog. A reserve line exists. A discount has no key to it. It is not a test for marks. It is a safety net, so “A reserve” 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: a reserve line

A practice 40 Kč. Write two things you MUST NOT REACH for, and one you may.

1. Do not reach: a discount, a magnet, a skin. Reach: a delay, a broken bottle, a higher entry.

2. A sentence out loud about reaching.

3. What happens to 40 if a problem does not come? Write a rule (for practice: return).

4. Split 40 on paper from W.

You count when a discount is not on the reaching list. If it is, you have no reserve. You have a second want.

Pocket money: Pocket money: 10 Kč for a copy, not for juice with a discount. 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: a till reserve is sacred until a teacher says the end. 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 reserve for a pass” is L, not a trip reserve. 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: a reserve for broken cups. A lemonade discount will not eat it. 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 a reserve — A reserve is for a problem. A discount is not a problem.” If they have no time, a slip in the notebook is enough. Stories and class chat are not enough.

A reserve ≠ want. 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: reach, or not?

A reserve 40.

1. A magnet −50% for 40. Reach?

2. A bus +35 a machine. Reach?

3. Entry +20. Reach?

4. The end of the trip, 40 left. What with no fight?

Now you 💪

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

1. A reserve ≠ want.
2. A discount does not reach it.
3. Leftover has a rule.

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

• A reserve = a problem, not an opportunity.
• A percent of the ceiling or a fixed number from an adult.
• An empty reserve is a dead plan.
• Leftover is not split quietly.
• Names in the examples (Sofie, Matyáš) 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 · Content usage terms