We have already learnt numbers up to 20. Now let us go further and explore numbers all the way up to 99! These bigger numbers are all around us — the number of pages in a book, the number of days in a season, or the number of students in a school.
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Key Concepts
Tens and Ones: Every two-digit number is made of tens and ones. For example, 35 means 3 tens and 5 ones. We can think of a ten as a bundle of 10 sticks.
Reading and Writing Numbers: We write the tens digit first, then the ones digit. 47 is written as "forty-seven."
Number Names 21 to 99: After twenty comes twenty-one, twenty-two ... twenty-nine, then thirty, thirty-one ... and so on up to ninety-nine.
Counting Forward and Backward: We can count forward (21, 22, 23 ...) or backward (30, 29, 28 ...).
Comparing Numbers: To compare two numbers, first look at the tens digit. The number with more tens is bigger. If tens are the same, look at the ones digit.
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Worked Examples
A jar has 4 bundles of 10 candies and 6 loose candies. What number is this?
4 tens + 6 ones = 46 candies.
Write the number 53 in words.
5 tens and 3 ones. Read as fifty-three.
Which is bigger — 67 or 76?
67 has 6 tens; 76 has 7 tens. Since 7 > 6, 76 is bigger.
Fill in the missing number: 44, 45, ___, 47.
Count forward: after 45 comes 46.
Arrange in order from smallest to biggest: 82, 29, 51.
Look at tens: 2 tens < 5 tens < 8 tens. Order: 29, 51, 82.
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Common mistakes
- Do not mix up tens and ones. 35 means 3 tens, NOT 5 tens.
- When writing number names, remember hyphen: twenty-one, thirty-five (not twentyone or thirtyfive).
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Summary
Numbers 21 to 99 are two-digit numbers made of tens and ones. We can read, write, count, compare, and order them. Knowing these numbers helps us in everyday counting tasks!