Now we go beyond 9! We learn to count, read, write, and compare numbers from 10 to 20. We also learn the idea of tens and ones.
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Key Concepts
Making 10: When we have 10 objects, we can group them into one bundle of ten.
- Tens and Ones: Every number from 11 to 19 has 1 ten and some ones.
- 13 = 1 ten + 3 ones
- 17 = 1 ten + 7 ones
- 20 = 2 tens + 0 ones
Number names (10–20): 10 = ten, 11 = eleven, 12 = twelve, 13 = thirteen, 14 = fourteen, 15 = fifteen, 16 = sixteen, 17 = seventeen, 18 = eighteen, 19 = nineteen, 20 = twenty.
Order: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.
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Count 13 mangoes. Bundle 10 together — that is 1 ten. The remaining 3 are ones. So 13 = 1 ten + 3 ones.
Write the number: 1 ten and 6 ones. Answer: 16 (sixteen).
What comes after 14? Count on one: 14, 15. Answer: 15.
Which is greater — 18 or 12? 18 comes after 12 on the number line, so 18 > 12.
Arrange from smallest to biggest: 20, 11, 15. Answer: 11, 15, 20.
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Common mistakes
- Eleven (11) and twelve (12) do not follow the pattern "teen" — learn them separately.
- 20 has 2 tens and 0 ones, not 1 ten and 10 ones.
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Summary
Numbers 10 to 20 are made of tens and ones. We can count, compare, and order them just like smaller numbers, and we write them using two digits.