Interest

Before we start

Five minutes before Lesson 1, no scoring.

1. 1. If a jar of 100 counters is a whole, how many is 10%? How many is 5%?
2. 2. Is it better for YOU to earn interest or to pay it? Why?
3. 3. A poster says 'grow your money fast!'. What would you want to know first?

Lesson 1. Five in every hundred

Goldie · 45 min · Build 1%, 5% and 10% from a hundred grid before using a percentage to find a small interest amount.

1. Shade 5 squares out of 100. What percentage is shaded?
2. On a fictional €100 balance, what is 5% in euros?
3. If 10% of €20 is €2, what is 5% of €20?
4. Is “5%” the same thing as “€5” for every starting balance? Explain.

Lesson 2. Interest for a saver

Goldie · 45 min · Describe interest as an amount an account may add under its terms.

1. On the stated €100 card, calculate one year's interest.
2. Closing balance?
3. €20 at 5% for one year gives how much interest?
4. Is 5% promised forever? Explain.

Lesson 3. Interest for a borrower

Goldie · 45 min · Calculate a simple total repayment and recognise that fees or timing can change actual costs.

1. Total repayment for the €100 card?
2. Cost of borrowing on A and B?
3. Which costs less if all other terms are the same?
4. Why would an adult need the full agreement, not only the weekly amount?

Lesson 4. Growth on growth

Goldie · 45 min · Explain compounding through two rounds and distinguish a smooth model from a real investment path.

1. Fill round 1 and round 2 balances.
2. Why is round 2 growth €11 rather than €10?
3. Compare €121 and €120.
4. Correct the claim “It will always grow 10% each year.”

Final mission. Read the whole claim

Goldie · 45 min · Ask evidence-based questions about an interest claim, identifying missing term, fees and uncertainty before calculating.

1. Under A's stated rules, what is 5% of €100 and the ending balance?
2. Circle the facts missing from B: term, fees, starting balance, colour of the poster.
3. Can you calculate B's exact ending balance from the information given? Why?
4. Write one question you would ask a trusted adult before accepting a money claim.

Extension. Same rate, different starting amount

Goldie · 45 min · Compare interest amounts fairly when starting balances differ, without confusing a larger euro gain with a higher rate.

1. Find the interest and closing balance on card A.
2. Find the interest and closing balance on card B.
3. Which card has the larger euro gain? Are their rates different?
4. A pupil says “B is the better rate because it adds more euros.” Correct the sentence.

Extension. One year or two?

Goldie · 45 min · Read the term of a simple-interest classroom card and calculate repeated fixed interest without silently compounding.

1. Fill the balances at start, end of year 1 and end of year 2.
2. How much interest was added altogether?
3. Does the second €5 come from €100 or €105 under this card's rule?
4. Why must you read the term and calculation rule before comparing cards?

Extension. The fee changes the result

Goldie · 45 min · Distinguish interest earned from the final balance after a stated fee.

1. What is the balance just after the interest is added?
2. What is the balance after the fee?
3. How much higher than the starting €100 is the final balance?
4. Explain why “I earned €5 interest” and “my balance rose €3” can both be true.

Extension. More euros, fewer choices?

Goldie · 45 min · Explain with a concrete fictional basket why a higher money balance does not always buy more things when prices also change.

1. How many €10 books can €100 buy?
2. How many €12 books can €105 buy, and how much is left?
3. The balance rose by how many euros?
4. Why did the number of whole books fall despite the higher balance?

My money reflection

A quiet close to the month.

1. How I'd explain interest to a younger child…
2. One question I'd ask about a 'grow your money' claim…
3. What 'growth on growth' means to me now…

Cut-out coins

Play money for the lessons and the mission — fictional, for practice only. Cut along the dashed circles; print one page per pair for extra coins.