08. Chapter Notes: Fun with Numbers (Numbers 21 to 99)

Introduction

Numbers are like magic—they help us count, measure, and play games!
Let’s explore the exciting world of numbers from 21 to 99 and discover how they can make everyday things even more fun.
Ready to start this number adventure?

Let’s start by understanding the number names for each of these two-digit numbers:

In a two-digit number, the first digit represents the tens place, and the second digit represents the ones place.
For example, in the number 56, 5 is in the tens place, and 6 is in the ones place.
Understanding place value helps us read and write numbers correctly.

We can compare two two-digit numbers by looking at the digit in the tens place first.
If the tens digits are different, the number with the greater tens digit is greater.
If the tens digits are the same, we compare the ones digits to determine which number is greater.
Examples:
45 and 63: Since 6 is greater than 4, therefore 63 is greater than 45.
78 and 74: Since 7 is the same in both numbers, we look at the ones place. 8 is greater than 4, so 78 is greater than 74.

Numbers 21 to 30 – Let’s Count

Numbers 21 to 30 are formed by adding the tens place (20, 30) to the units place (1 to 10).
For example, 21 is formed by adding 20 and 1, 22 is formed by adding 20 and 2, and so on.
Practice counting from 21 to 30 to become familiar with these numbers.

Numbers 31 to 40 – One More Ten

Numbers 31 to 40 follow a similar pattern.
They are formed by adding the tens place (30) to the units place (1 to 10).
For example, 31 is formed by adding 30 and 1, 32 is formed by adding 30 and 2, and so on.
Practice counting from 31 to 40 to get comfortable with these numbers.

Numbers 41 to 50 – Moving Forward

Numbers 41 to 50 are created by adding the tens place (40) to the units place (1 to 10).
For example, 41 is formed by adding 40 and 1, 42 is formed by adding 40 and 2, and so on.
Practice counting from 41 to 50 to reinforce your understanding.

Numbers 51 to 60 – Climbing Higher

Numbers 51 to 60 continue the pattern.
They are formed by adding the tens place (50) to the units place (1 to 10).
For example, 51 is formed by adding 50 and 1, 52 is formed by adding 50 and 2, and so on.
Practice counting from 51 to 60 to become proficient with these numbers.

Numbers 61 to 70 – A New Set

Numbers 61 to 70 are formed by adding the tens place (60) to the units place (1 to 10).
For example, 61 is formed by adding 60 and 1, 62 is formed by adding 60 and 2, and so on.
Practice counting from 61 to 70 to strengthen your knowledge.

Numbers 71 to 80 – Further Exploration

Numbers 71 to 80 follow the same pattern.
They are formed by adding the tens place (70) to the units place (1 to 10).
For example, 71 is formed by adding 70 and 1, 72 is formed by adding 70 and 2, and so on.
Practice counting from 71 to 80 to become more confident.

Numbers 81 to 90 – Nearing the End

Numbers 81 to 90 are created by adding the tens place (80) to the units place (1 to 10).
For example, 81 is formed by adding 80 and 1, 82 is formed by adding 80 and 2, and so on.
Practice counting from 81 to 90 to solidify your understanding.

Numbers 91 to 99 – The Final Stretch

Numbers 91 to 99 follow the same pattern as the previous sets.
They are formed by adding the tens place (90) to the units place (1 to 9, as there is no 0 in the units place).
For example, 91 is formed by adding 90 and 1, 92 is formed by adding 90 and 2, and so on.
Practice counting from 91 to 99 to master these numbers.

The number 10 is the first and the smallest two-digit number.

Example 1:

Now make a group of 10 pencils.
We can make only 1 group. It represents 1 Ten. But there is no single pencil remaining. It indicates 0 ones.
So, the number 10 can write as:

Example 2:

If we take 21 pencils, we can make 2 groups of 10 pencils that can be represented as 2 Tens.
1 remaining pencil can be represented as 1 Ones.
2 Tens and 1 Ones = 21
We can write 21 as: