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Maths History

Roman market maths

Create shopping and counting challenges using I, V, X, L and C in a Roman marketplace.

Quick answer

Roman market maths is the fun way to learn counting and basic arithmetic using Roman numerals (I, V, X, L, C) from the ancient Roman marketplace. You can count, add, and subtract items using Roman numerals just like people did over 2,000 years ago!

Learning outcome

By the end of this page, you will be able to count and add items using Roman numerals up to 100, just like a Roman merchant would have done in the marketplace. Success signs:
  • You can read and write Roman numerals from 1 to 100
  • You can add small numbers using Roman numerals
  • You can solve simple shopping problems using Roman numerals
  • You can imagine how Roman merchants might have used maths to trade

Why this matters

Learning Roman market maths helps you understand how people used maths long before calculators and computers. It shows that maths is useful for trading, counting goods, and solving everyday problems – just like it was in ancient Rome. You'll also learn to think in different ways about numbers, which makes your brain stronger!

How it works

Roman numerals are made using letters:
  • I = 1
  • V = 5
  • X = 10
  • L = 50
  • C = 100
To write numbers, we put letters together. When a smaller letter is before a bigger one, we subtract. When a smaller letter is after a bigger one, we add.

Examples you can see

Let's look at how Romans counted and added things: Counting in Roman numerals
  • 1 = I
  • 2 = II
  • 3 = III
  • 4 = IV (1 before 5 means 5 - 1 = 4)
  • 5 = V
  • 6 = VI (5 + 1 = 6)
  • 7 = VII (5 + 2 = 7)
  • 8 = VIII (5 + 3 = 8)
  • 9 = IX (1 before 10 means 10 - 1 = 9)
  • 10 = X
Adding in Roman numerals Let's say you have 3 apples (III) and your friend gives you 5 more (V). How many apples do you have? III + V = VIII (3 + 5 = 8) Shopping example In a Roman market, a merchant sells:
  • 2 loaves of bread = II
  • 3 pieces of cheese = III
  • 4 olives = IV
How many items did the merchant sell in total? II + III + IV = IX (2 + 3 + 4 = 9 items)

Try it as a mini adventure

The Roman Market Challenge You are a young Roman merchant helping your family sell goods at the market. You have a basket of items to sell. Here's your shopping list: 1st time: 3 apples (III) 2nd time: 2 oranges (II) 3rd time: 5 grapes (V) 4th time: 1 loaf of bread (I) 5th time: 4 dates (IV) How many items do you have in total? Answer: III + II + V + I + IV = XIII (3 + 2 + 5 + 1 + 4 = 15 items) Now, imagine you have 10 coins (X) and you buy 4 items (IV). How many coins do you have left? Answer: X - IV = VI (10 - 4 = 6 coins)

Common mistakes

  • Mistake: Writing IV as IIII for 4
    Why it happens: Confusing the rule of subtracting letters
    Fix: Remember that when a smaller letter comes before a larger one, you subtract. So IV = 5 - 1 = 4
  • Mistake: Writing 6 as VV instead of VI
    Why it happens: Thinking you can just add letters without following rules
    Fix: 6 = 5 + 1 = VI (not V + V = 10)
  • Mistake: Adding 9 + 3 = XII (instead of 12)
    Why it happens: Not knowing that 9 = IX
    Fix: IX + III = XII (9 + 3 = 12)

Parent and carer guide

How to help your child with Roman market maths 1. Start with simple counting: Use small objects like coins or blocks to practice counting in Roman numerals 1 to 10. 2. Play a Roman shopping game: Set up a pretend market with items labeled in Roman numerals. Have your child add up what they buy. 3. Practice with real examples: When you're out shopping, count items using Roman numerals (e.g., "We have III items in our basket"). 4. Be patient: Roman numerals can be tricky at first. Encourage your child to write them out and check their work. 5. Don't worry about mistakes: If your child writes 4 as IIII, gently remind them that IV means 5 - 1 = 4. 6. Use the real-world connection: Explain that Romans used these same maths to trade goods, just like we do today. 7. Make it fun: Turn counting into a game or story. For example, "You are the Roman merchant who sells 7 eggs today!"

Practice questions

  1. What is 3 + 4 in Roman numerals?
  2. How many items are in II + V + III?
  3. What is 8 - 3 in Roman numerals?
  4. Write 12 in Roman numerals
  5. What is 10 - 6 in Roman numerals?
Answers:
  1. IV + III = VII (4 + 3 = 7)
  2. II + V + III = X (2 + 5 + 3 = 10)
  3. VIII - III = V (8 - 3 = 5)
  4. XII
  5. X - VI = IV (10 - 6 = 4)

FAQ

What are Roman numerals used for today?

Roman numerals are still used today for things like clocks, book chapters, movie release years, and page numbers in prefaces.

Why did Romans use these letters?

Romans used letters because they had no written numbers like we do. The letters I, V, X, L, C were chosen because they were easy to write and understand.

Can you make big numbers with Roman numerals?

Yes! You can make big numbers by combining letters. For example, 100 = C, 500 = D, 1000 = M. But we usually only use I, V, X, L, C for simple market maths.

How do you write 0 in Roman numerals?

Romans did not have a symbol for zero. They didn't need it for their counting system.

Are Roman numerals harder than our numbers?

They can be harder at first because you need to understand when to add and when to subtract. But with practice, they're just as useful!