Roman numerals use letters: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. Usually the symbols go from largest to smallest and you add them: XXVII = 27. When a smaller symbol comes just before a larger one, take it away: IV = 4, IX = 9, XL = 40, XC = 90. To write a number, split it by place value and write each part.
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Maths you can move
Build 8 + 5
Tap two gold counters to fill the ten-frame.
8 in the frame + 5 waiting. The total stays the same.
Words to know
- Roman numeral
- a number written with the letters I, V, X, L, C, D and M
- subtractive pair
- a smaller symbol before a larger one, like IV = 4
Worked examples
What number is XXVII?
- 1.X + X + V + I + I.
- 2.10 + 10 + 5 + 1 + 1 = 27.
= 27
What number is XLIV?
- 1.XL = 50 − 10 = 40 and IV = 5 − 1 = 4.
- 2.40 + 4 = 44.
= 44
Write 1994 in Roman numerals.
- 1.1994 = 1000 + 900 + 90 + 4.
- 2.M + CM + XC + IV.
= MCMXCIV
For parents
Method: Add, but take away a smaller symbol written before a larger one
What to say: Are the symbols getting smaller? Is a smaller one sitting before a larger one?
Common mistakes:
- Ignores the subtraction rule: adds every symbol when reading, and writes 4s and 9s by repeating symbols.
- Mixes up the values of V (5) and X (10).
- Mixes up the values of L (50) and C (100).
- Takes away a smaller symbol that comes AFTER a larger one (reads VII as 3 and LX as 40).