十一 · 二十 · 九十九
Build 11–99 from 1–10: a number after 十 is added, a number before 十 multiplies it
Structure
十 + 数字 · 数字 + 十 · 数字 + 十 + 数字
What it means
Numbers from 11 to 99 are built from 1–10: a number after 十 is added, a number before 十 multiplies it.
How it is built
十 + number = 10 + n: 十二 (12). Number + 十 = n × 10: 二十 (20). Number + 十 + number: 九十九 (99). 是十八吗？——不是，是八十！ (Is it 18? — No, 80!)
When to use it
Use them for counting, ages and prices. Say the number the way it is built: 三十五 = three tens and five (35).
Watch out
十八 (18) and 八十 (80) are different numbers, so watch the order. For 10–19 just start with 十: ✗ 一十五 ✓ 十五 (15).
Examples
十一、十二、十三……十九
11, 12, 13 … 19
二十、三十、四十……九十
20, 30, 40 … 90
是十八吗？——不是，是八十！
Is it 18? — No, 80!
Learn this in 启蒙 · Lesson 4: 一二三四五 (Numbers and first strokes)
A dialogue, a reading, word cards with audio and a drill that uses it, in Learn Chinese with Bao. The first lessons of every level are free.
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