Class 1 Exam  >  Class 1 Notes  >  Mathematics for Class 1: NCERT (Joyful-Mathematics)  >  Chapter Notes: Fun with Numbers (Numbers 21 to 99)

Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths

Introduction


In this chapter, we will explore numbers from 21 to 99. These numbers are composed of two digits and are essential for understanding larger numbers. We will learn how to read and write them, as well as their place value.

Number Names (21 to 99)

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

Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths

Place Value (Tens and Ones)

  • 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.

Counting (Skip Counting by Tens):

  • We can count from 20 to 99 by adding 10 each time.
  • For example, 20, 30, 40, 50, 60, 70, 80, 90.

Comparison of Numbers (Greater Than and Less Than):

  • 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.

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.

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.

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.

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.

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.

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.

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.

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.

What is the Ones and Tens Concept?

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

Example 1:

  • Let’s take 10 pencils.
Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths
  • Now make a group of 10 pencils.Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths
  • 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:

Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths

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.Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths
  • 2 Tens and 1 Ones = 21
  • We can write 21 as:

Fun with Numbers (Numbers 21 to 99) Class 1 Notes MathsExample 3:

  • We can represent 100 as 10 groups of Tens.Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths
  • We cannot write 100 as:Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths
  • We use the hundreds place. The number 100 is written as:Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths

100 is the first and smallest three-digit number.

Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths

Let's calculate the number of popsicles given in the table below

Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths

Missing Numbers


A series or sequence where a number is missed is known as a missing number sequence.
Look at the example given below. 

Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths

The document Fun with Numbers (Numbers 21 to 99) Class 1 Notes Maths is a part of the Class 1 Course Mathematics for Class 1: NCERT (Joyful-Mathematics).
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