XXV in Numbers — Roman Numeral XXV = 25

XXV is read left to right, adding the values of each symbol:

Symbol | Value X | 10 X | 10 V | 5

Total: 10 + 10 + 5 = 25

Why is it additive here? When a symbol of equal or lesser value follows the previous symbol, the values are added. • X followed by X: 10 + 10 = 20 (additive, same value) • X followed by V: V < X, so add → 20 + 5 = 25 (additive)

Result: XXV = 25

The seven basic Roman numeral symbols:

Symbol | Value I | 1 V | 5 X | 10 L | 50 C | 100 D | 500 M | 1000

Memory tip: 'I Value Xylophones, Lucy Can't Dance Much' (I=1, V=5, X=10, L=50, C=100, D=500, M=1000)

Subtractive notation is used when a smaller symbol appears before a larger one — the smaller is subtracted:

Allowed subtractive pairs: • IV = 5 − 1 = 4 • IX = 10 − 1 = 9 • XL = 50 − 10 = 40 • XC = 100 − 10 = 90 • CD = 500 − 100 = 400 • CM = 1000 − 100 = 900

Rules:

1. Only I, X, and C can be used as subtractive numerals.
2. I can only be subtracted from V and X.
3. X can only be subtracted from L and C.
4. C can only be subtracted from D and M.
5. Never subtract more than one symbol at a time (e.g., IIX is NOT valid; use VIII = 8).
6. The same symbol cannot be repeated more than three times in a row.

Number | Roman Numeral 1 | I 2 | II 3 | III 4 | IV 5 | V 6 | VI 7 | VII 8 | VIII 9 | IX 10 | X 11 | XI 12 | XII 13 | XIII 14 | XIV 15 | XV 16 | XVI 17 | XVII 18 | XVIII 19 | XIX 20 | XX 21 | XXI 22 | XXII 23 | XXIII 24 | XXIV 25 | XXV 26 | XXVI 27 | XXVII 28 | XXVIII 29 | XXIX 30 | XXX

Step-by-step method to convert any Roman numeral:

1. Write the values of each symbol: X=10, X=10, V=5.
2. Check for subtractive pairs: if a symbol is less than the one to its right, subtract it; otherwise add it. • X and X: X is NOT less than X → add: 10 + 10 = 20 • X and V: V IS less than X — but here V comes AFTER X, so no subtraction applies. We only subtract when the smaller comes BEFORE the larger. • X → V: V < X, but V is to the right of X, so add: 20 + 5 = 25.
3. Result: XXV = 25.

General algorithm: • Scan left to right. • If current symbol ≥ next symbol → add current value to total. • If current symbol < next symbol → subtract current value from total.

Example check with XXIV (24): X + X + (V before…wait: X=10, X=10, I=1, V=5) → 10, 10, and IV = 4 → 10 + 10 + 4 = 24 ✓