Imagine you have a box of blocks.

Some blocks have the letter "I" on them, some have "V", some have "X", some have "L", some have "C", some have "D", and some have "M".

Each letter is a special code that stands for a number.

"I" is 1, "V" is 5, "X" is 10, "L" is 50, "C" is 100, "D" is 500, and "M" is 1,000.

Now, if you want to show the number 2, you just need to put two "I" blocks together like "II".

If you want to show 6, you can put a "V" block and an "I" block together like "VI".

But what if you want to show 4?

You could use four "I" blocks like "IIII", but there's a special rule.

If you put a smaller number in front of a bigger number, it means you subtract the smaller one.

So, for 4, you put an "I" in front of a "V" to make "IV".

Traditionally, the largest number you can write in Roman numerals is 3,999 which is MMMCMXCIX.

You can represent numbers larger than this in Roman numerals using an overline (known as the vinculum or virgula).

And that's how you can make any number with your blocks!