SUBTRACTIVE NOTATION

Understand subtractive notation - why IV means 4 and IX means 9.

L4L5

Section 1 / 2

THE SUBTRACTIVE RULE

Instead of writing IIII for 4, the Romans placed I before V to mean 5−1=4, giving IV. This subtractive notation keeps numbers shorter. It only applies in specific cases: I before V(4) or X(9), X before L(40) or C(90), C before D(400) or M(900).

IV = ?

1I before V means 5 − 1 = 4

2IV = 4 (NOT IIII)

= 4

IX = ?

1I before X means 10 − 1 = 9

= 9

XL = ?

1X before L means 50 − 10 = 40

= 40

LEADER TIP

The rule: a smaller numeral before a larger one means subtract. IV = 5-1 = 4. Only certain combinations are allowed.

BEFORE THIS LESSON, TRY

Converting Numerals

PRACTICE WITH THESE GAMES

Sort Numbers

Subtraction Table

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CONTINUE WITH:

Large Numbers

SUBTRACTIVE NOTATION

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SUBTRACTIVE NOTATION