A find under the bed

Erklärus rummaged under his bed and pulled out a little tin. Something jingled inside it.

Liri: “What is that jingling? And what are these round, shiny things anyway?”
Erklärus: “That’s money. We humans came up with the idea: for these coins and notes you get things – a loaf of bread, a book, a ticket for a rocket. Everyone believes that they have a value, and that’s why we swap them for things.”
Liri: “So money is a kind of… promise?”
Erklärus: “Exactly. And like every promise, it has clear rules. This is my pocket money. Would you like to learn how to do sums with it?”
Erklärus: “The most important rule first: we don’t mix euros and cents. Either we calculate with euros, or we calculate with cents – never both at the same time with a decimal point.”

🪙 Getting to know coins and notes

These are the coins and small notes you need to know:

1c
2c
5c
10c
20c
50c
€1
€2
€5
€10
€20

💰 Making amounts – with as few coins and notes as possible

Erklärus wants to lay down 7 euros – but with as few coins and notes as possible.

Erklärus: “A 5-euro note and a 2-euro coin. That’s only two pieces of money – far fewer than seven single 1-euro coins!”
Liri: “But how do you know straight away that this is the fewest pieces?”
Erklärus: “There’s a fixed rule for that!”
📐 The rule

Step 1: Always take the biggest coin or note that still fits into the amount, without going over.
Step 2: Look at what is left over, and again take the biggest coin or note that still fits. Repeat this until nothing is left.

An example with 17 euros: the biggest piece that fits is the 10-euro note (a 20 would be too much). That leaves 7 euros – the biggest piece that fits for that is the 5-euro note. That leaves 2 euros – exactly right for the 2-euro coin. Done: only 3 pieces!

How would you make 12 euros with as few notes and coins as possible?

A 10-euro note + a 2-euro coin (2 pieces)
Two 5-euro notes + two 1-euro coins (4 pieces)
Twelve 1-euro coins (12 pieces)

🛍️ The jumble sale in Erklärus’s room

Liri doesn’t go to school – so Erklärus simply brings school to her. He spreads a few old things out on the carpet: a pencil, a book, his old telescope. A little jumble sale, right in the middle of his room.

Liri plays the shopkeeper, Erklärus is the customer.

Liri: “This pencil costs 4 cents.”
Erklärus: “I only have a 5-cent coin with me.” (pays with 5c)
Liri: “Then you get change back!”
5c − 4c =
🛍️ Exercise 1 – Cents
A rubber costs 8 cents. You pay with a 10-cent coin. How many cents do you get back?
🛍️ Exercise 2 – Euros
A book about space costs 6 euros. You pay with a 10-euro note. How many euros do you get back?
💰 Exercise 3 – Adding up
You have a 5-euro note and a 2-euro coin. How many euros do you have altogether?
🌌 Just for fun: money in space

A ticket for a space-tourism flight often costs several million euros – so much that we can hardly imagine it.
Luckily, a few cents and euros are enough for our exercises – just like at the jumble sale!

❌ Common mistake

Euros and cents are sometimes mixed up, even though they should be kept strictly apart – for example, writing “3 euros and 50 cents” as “3.50” comes later. In Grade 1 the rule is: only whole-euro exercises or only whole-cent exercises, never mixed with a decimal point!

The tin has been counted empty

Liri had sorted, counted and added up every coin in the tin.

Liri: “Money is really just mathematics that you can touch.”
Erklärus: “That’s exactly why people like practising with it. You can see straight away whether the sum is right.”
Liri: “This sum isn’t for the way home – but I’ll write it in my book anyway. You never know what you’ll still need on the way.”
“Calculating with money: never mix euros and cents. Make amounts with as few coins and notes as possible. Change = amount paid minus price.”
What you learned today
Paid − price = change
Always calculate euros and cents separately – never mix them with a decimal point
🌟

Chapter 6 mastered!

Erklärus and Liri can now count money, make amounts and work out change.

Erklärus’s notebook – page 6:
“Money: never mix euros and cents. Make amounts with as few coins and notes as possible. Change = amount paid minus price. At a jumble sale you learn subtraction without even noticing!”
← Back to overview 6 – Money