 Roman Numerals I to C | Year 4 Maths Resources | KS2 Revision

## What you need to know

Things to remember:

• If there is an I before a V or X it means subtract 1.
• If there is an X before L or C it means subtract 10.
• You should start by looking for any subtractions first.

Where we use 10 numbers to make up all other numbers, the Romans used a combination of 7 letters to write theirs. We will look at 5 of those letters:

Roman Numerals I V X L C

Numbers 1 5 10 50 100

The Romans had rules for how they wrote their numbers.

Rule 1: Big Numbers Before Small, Add Them All Together

II

$$1+1=2$$

III

$$1+1+1=2$$

VIII

$$5+1+1+1=8$$

XVII

$$10+5+1+1=17$$

XXXVI

$$10+10+10+5+1$$

CLII

$$100+50+1+1=152$$

The Romans didn’t like to put four of the same letter next to each other, so how could they write the number 4? They had subtraction rules.

Rule 2: If there is an I before a V or an X, we subtract 1.

IV

$$5-1=4$$

IX

$$10-1=9$$

Rule 3: If there is an X before an L or a C, we subtract 10.

XL

$$50-10=40$$

XC

$$100-10=90$$

We can use these rules to make our numbers up to 100. We just need to remember Rules 2 and 3.

4 = IV

9 = IX

40 = XL

90 = XC

XXIV

$$10+10+5-1=24$$

LXXVI

$$50+10+10+5+1=76$$

LXXIX

$$50+10+10+10-1=79$$

We don’t just read Roman Numerals, but we also need to know how to write them.

“What is 97 in Roman Numerals?”

We can do this in 3 steps.

Step 1: Think about how to write the tens:

90 = XC

Step 2: Think about how to write the units:

7 = VII

Step 3: Put Steps 1 and 2 together:

97 = XCVII

## Example Questions

Remember, an I before a V means subtract 1, and an X before and L means subtract 10.

XL = 50 – 10 = 40

IV = 5 – 1 = 4

After putting these together, we get that XLIV = 44.

90 = XC

Do the units:

9 = IX

Put them together:

99 = XCIX

99 in Roman Numerals is XCIX.

## KS2 SATs Flash Cards

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