☰ Contents · Mathematics

Value of expressions, properties of operations, Roman numerals

Lessons 133–136 · 4 lessons · I.V. Repyova, Y.V. Zemlina. Mathematics Grade 1, Parts 1–4. Novda Edutainment, 2023
136

Roman numerals

Textbook Part 4, pp. 52–53
GoalRead and write the Roman numerals I, V, X, L; use them for centuries and clock faces.
New words
Roman numerals · rim raqamlaricentury · asrclock face · siferblat
Explanation

Roman numerals: I = 1, V = 5, X = 10, L = 50, C = 100. A smaller numeral after a bigger one is added: VI = 5 + 1 = 6, XII = 12. Before it, it is subtracted: IV = 5 − 1 = 4, IX = 10 − 1 = 9. Centuries and clock faces often use Roman numerals.

Worked examples
We live in the XXI (21st) century. Abu Ali ibn Sina lived in the XI (11th) century.
XX = 20, XL = 40, LX = 60, LXX = 70.
Class activity

Matchstick puzzle: build “VI − IV = IX” with sticks. Remove one stick to make it true. (For example: VI − IV = II.)

Practice
1
VII = ?
2
IX = ?
3
Write 15 in Roman numerals.
4
Compare: XI ... IX