Class 1 — Mathematics

Numbers 1 to 99

Class 1

✓By the end of this lesson students will be able to count objects up to 99.
✓By the end of this lesson students will be able to identify numbers that come before, after, and between given numbers up to 99.
✓By the end of this lesson students will be able to write number names for numbers up to 99.
✓By the end of this lesson students will be able to understand the sequence of numbers from 1 to 99.

Key concepts

Counting Numbers 1 to 99

Counting is finding out 'how many' objects there are in a group. We count numbers in a specific order, starting from 1. For larger numbers, we can group objects into tens and ones to make counting easier. For example, 3 tens and 5 ones make 35.

Before, After, and Between Numbers

When we count numbers in order:\n* The number that comes 'just before' a given number is one less than that number.\n* The number that comes 'just after' a given number is one more than that number.\n* The number that comes 'between' two given numbers is the number that is greater than the first number and smaller than the second number.

Number Names (1 to 99)

Number names are the words we use to write numbers. For example, 'one' for 1, 'ten' for 10, 'twenty-five' for 25. It is important to learn the spellings of these number names. Numbers from 21 to 99 (excluding multiples of 10) are written with a hyphen, e.g., 'thirty-two', 'forty-nine'.

Key facts to remember

1Numbers tell us 'how many' objects there are.
2We count numbers in a fixed sequence: 1, 2, 3, and so on.
3The number that comes 'just before' a given number is one less than it.
4The number that comes 'just after' a given number is one more than it.
5Numbers like 10, 20, 30, 40, 50, 60, 70, 80, 90 are called 'tens'.
6Number names are the word forms of numbers.
7For numbers from 21 to 99 (except multiples of 10), we use a hyphen in their number names (e.g., forty-five).

Worked examples

Example 1

Count the total number of pencils shown below: (Imagine 4 bundles of 10 pencils each and 7 loose pencils).

IStep 1: Count the bundles of ten pencils. There are 4 bundles. So, 4 tens = 40 pencils.

IIStep 2: Count the loose pencils. There are 7 loose pencils. So, 7 ones = 7 pencils.

IIIStep 3: Add the tens and ones together: 40 + 7 = 47.

Answer

47 pencils

Grouping into tens and ones helps in counting larger numbers quickly.

Example 2

Fill in the blanks: \na) The number just after 59 is ____.\nb) The number just before 81 is ____.\nc) The number between 65 and 67 is ____.

Ia) To find the number just after 59, we count one more than 59. So, 59 + 1 = 60.

IIb) To find the number just before 81, we count one less than 81. So, 81 - 1 = 80.

IIIc) To find the number between 65 and 67, we count from 65. The next number is 66. We check if 66 is before 67. Yes, it is. So, 66 is the number between 65 and 67.

Answer

a) 60\nb) 80\nc) 66

Think of counting forwards or backwards on a number line.

Example 3

a) Write the number name for 73.\nb) Write the number for 'Ninety-six'.

Ia) For the number 73: The tens digit is 7, which is 'Seventy'. The ones digit is 3, which is 'three'. Combining them gives 'Seventy-three'.

IIb) For 'Ninety-six': 'Ninety' means 9 tens. 'six' means 6 ones. Combining 9 tens and 6 ones gives the number 96.

Answer

a) Seventy-three\nb) 96

Remember to use a hyphen for number names like twenty-one, thirty-five, etc.

Common mistakes

✗Confusing the number that comes 'before' with the number that comes 'after'.
✗Incorrectly spelling number names, especially for numbers like 'twelve', 'fifteen', 'forty', 'ninety'.
✗Skipping numbers or repeating numbers while counting in sequence.
✗Not understanding the concept of tens and ones when counting or writing numbers beyond 20.

Exam tips

★Always count carefully, one by one, or by grouping tens, to ensure accuracy.
★Practice writing number names and their spellings regularly.
★Use a number line or a hundred chart to visualise and find 'before', 'after', and 'between' numbers.
★Read the question carefully to understand exactly what is being asked before attempting to answer.

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