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.
  • Add after subtracting.

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

Question 1: What is XLIV in numbers?

Answer

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.

Question 2: What is 99 in Roman Numerals?

Answer

Start with the tens:

 

90 = XC

 

Do the units:

 

9 = IX

 

Put them together:

 

99 = XCIX

 

99 in Roman Numerals is XCIX.