Rule 1: Adding Values

When a smaller letter comes after a bigger letter, you add the values.

• II = 1 + 1 = 2
• VI = 5 + 1 = 6
• XI = 10 + 1 = 11

Rule 2: Subtracting Values

When a smaller letter comes before a bigger letter, you subtract the smaller from the bigger.

• IV = 5 - 1 = 4
• IX = 10 - 1 = 9
• XL = 50 - 10 = 40
• XC = 100 - 10 = 90
• CM = 1000 - 100 = 900

Rule 3: Combining the Rules

You can combine both rules to form larger numbers.

• XIV = 10 + (5 - 1) = 14
• XXVII = 10 + 10 + 5 + 2 = 27
• MCMXC = 1000 + (1000 - 100) + (100 - 10) = 1990

Write the Roman numeral MCDXXVII as a number.

Break it down step by step:

• M = 1000
• CD = 400 (500 - 100)
• XX = 20 (10 + 10)
• VII = 7 (5 + 1 + 1)

Now add them together:

$1000 + 400 + 20 + 7 = 1427$

So, MCDXXVII = 1427

• Memorise the seven basic symbols (I, V, X, L, C, D, M)
• Remember: smaller before bigger means subtract
• Look for real examples like clock faces or chapter numbers in books

In Tanzania, you can see Roman numerals on some clock faces at school, on old church bells, or on the pages of books where chapter numbers are written. For example, if you are reading a novel and see "Chapter X" on a page, you now know it means Chapter 10. This helps you read and understand important numbers in everyday life, even when they are written in this old but still useful style.