What you need to know

Things to remember:

• Break up the numerals into parts and change each part into numbers

Where we use 10 numbers to make up all other numbers, the Romans used a combination of 7 letters to write theirs. We have previously just looked at 5 of these, but here we will look at all 7

Roman Numerals       I           V         X         L          C          D         M

Numbers1                   1          5          10        50        100      500      1000

We previously learned about an important rule, that if there is an I before a V or an X, we subtract 1.

IV

$$5-1=4$$

IX

$$10-1=9$$

We do something similar with a C before a D or an M, but instead of subtracting 1 we subtract 100.

CD

$$500-100=400$$

CM

$$1000-100=900$$

Now that we know these, we can put this together with the previously rule we learned about converting Roman numerals into numbers.

What is DLXIV in numbers?

D = 500

L = 50

X = 10

I = 1

V = 5

Now we need to add these together. But we need to be careful, the 1 before the 5 means that we subtract this.

DLXIV = 500 + 50 + 10 + 5 -1 = 564

What is DCCCXXXVIII in numbers?

D = 500

C = 100

C = 100

C = 100

X = 10

X = 10

X = 10

V = 5

I = 1

I = 1

I = 1

We don’t have any smaller numbers before big numbers, so we can just do lots of adding!

DCCCXXXVIII = 500 + 100 + 100 + 100 + 10 + 10 + 10 + 5 + 1 + 1 + 1 = 838

What is 495 in roman numerals?

Step 1: Figure out how to write the hundreds, tens, and units in roman numerals.

400 = CD

90 = XC

5 = V

Step 2: Put everything together.

495 = CDXCV

What is 678 in roman numerals?

Step 1: Figure out how to write the hundreds, tens, and units in roman numerals.

600 = DC

70 = LXX

8 = VIII

Step 2: Put everything together.

678 = DCLXXVIII

Example Questions

Question 1: What is DCXXXIX in numbers?

D = 500

C = 100

X = 10

X = 10

X = 10

I = 1

X = 10

We have a 1 before a 10, so we need to subtract this and add everything else.

DCXXXIX = 500 + 100 + 10 + 10 + 10 + 10 – 1 = 639

Question 2: What is 888 in roman numerals?

Step 1: Figure out how to write the hundreds, tens, and units in roman numerals.

800 = DCCC

80 = LXXX

8 = VIII

Step 2: Put everything together.

888 = DCCCLXXXVIII