Addition & Numbers 171-180 Basic 1 Mathematics Lesson Note

Subject: Mathematics
Class: Primary 1
Topic: Addition & Numbers 171-180
Duration: 35 minutes

Learning Objectives

By the end of this lesson, pupils should be able to:

• Count numbers from 171 to 180
• Count in 2s and 3s
• Write numbers 171-180
• Add two 2-digit numbers with sum not more than 50

1. COUNTING SKILLS: Numbers 171-180

Let’s Learn 171 to 180: 

171 – ONE HUNDRED AND SEVENTY-ONE 

172 – ONE HUNDRED AND SEVENTY-TWO 

173 – ONE HUNDRED AND SEVENTY-THREE 

174 – ONE HUNDRED AND SEVENTY-FOUR 

175 – ONE HUNDRED AND SEVENTY-FIVE 

176 – ONE HUNDRED AND SEVENTY-SIX 

177 – ONE HUNDRED AND SEVENTY-SEVEN 

178 – ONE HUNDRED AND SEVENTY-EIGHT 

179 – ONE HUNDRED AND SEVENTY-NINE 

180 – ONE HUNDRED AND EIGHTY

Exercise 1: Count from 171 to 180: 171, 172, 173, 174, 175, 176, 177, 178, 179, 180

Exercise 2: Fill in the missing numbers:

1. 171, 172, ___, 174, ___
2. 175, ___, 177, ___, 179
3. 173, 174, ___, 176, ___

Exercise 3: What comes next?

1. 170, 171, ___
2. 176, 177, ___
3. 178, 179, ___

2. COUNT IN 2s AND 3s

Counting in 2s: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30

Exercise 4: Count in 2s:

1. 2, 4, ___, 8, ___
2. 12, 14, ___, 18, ___
3. 20, 22, ___, 26, ___

Exercise 5: Continue counting in 2s:

1. 6, 8, 10, ___, ___, ___
2. 16, 18, 20, ___, ___, ___

Counting in 3s: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30

Exercise 6: Count in 3s:

1. 3, 6, ___, 12, ___
2. 15, 18, ___, 24, ___
3. 9, 12, ___, 18, ___

Exercise 7: Continue counting in 3s:

1. 3, 6, 9, ___, ___, ___
2. 18, 21, 24, ___, ___

3. WRITING SKILLS: Numbers 171-180

Practice Writing Numbers 171-180:

Exercise 8: Trace these numbers: 171 171 171 172 172 172 173 173 173 174 174 174 175 175 175

Exercise 9: Trace these numbers: 176 176 176 177 177 177 178 178 178 179 179 179 180 180 180

Exercise 10: Write these numbers:

1. One hundred and seventy-two: ___
2. One hundred and seventy-six: ___
3. One hundred and eighty: ___
4. One hundred and seventy-four: ___

Exercise 11: Complete the sequence: 170, ___, 172, ___, 174, ___, 176, ___, 178, ___, 180

4. ADDITION: Two 2-Digit Numbers (Sum ≤ 50)

Adding 2-Digit Numbers: When we add two 2-digit numbers, we add the ones first, then the tens.

Examples:

• 12 + 15 = 27
• 20 + 18 = 38
• 14 + 23 = 37
• 25 + 13 = 38

Exercise 12: Add these 2-digit numbers:

1. 11 + 12 = ___
2. 13 + 14 = ___
3. 15 + 16 = ___
4. 20 + 18 = ___
5. 22 + 15 = ___

Exercise 13: Find the sum:

1. 10 + 25 = ___
2. 14 + 21 = ___
3. 16 + 12 = ___
4. 23 + 11 = ___

Exercise 14: Complete the addition:

1. 🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀 + 🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀🏀 = ___ (12 + 15)
2. ⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐ + ⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐ = ___ (14 + 21)

Exercise 15: Step-by-step addition:

1. 13 + 24 = ? Add ones: 3 + 4 = ___ Add tens: 10 + 20 = ___ Total: ___ + ___ = ___
2. 16 + 22 = ? Add ones: 6 + 2 = ___ Add tens: 10 + 20 = ___ Total: ___ + ___ = ___

Exercise 16: Word problems:

1. Tom has 15 marbles. His friend gives him 12 more marbles. How many marbles does Tom have now? 15 + 12 = ___
2. There are 18 girls and 16 boys in the class. How many children are there in total? 18 + 16 = ___
3. Mary collected 23 shells. Her sister collected 14 shells. How many shells did they collect together? 23 + 14 = ___

Exercise 17: Check your addition:

1. 14 + 25 = 39 (True/False) ___
2. 12 + 17 = 29 (True/False) ___
3. 21 + 18 = 40 (True/False) ___
4. 15 + 24 = 39 (True/False) ___

Exercise 18: Find the missing number:

1. 12 + ___ = 30
2. ___ + 15 = 35
3. 18 + ___ = 40
4. ___ + 22 = 45

Homework

1. Practice counting from 171 to 180
2. Write numbers 171-180 three times each
3. Practice counting in 2s and 3s up to 30
4. Practice adding two 2-digit numbers with sums up to 50
5. Create 3 addition word problems using objects at home

Teacher: Use base-10 blocks or counting materials to help pupils visualize 2-digit addition