➕➖ Addition and Subtraction

In this lesson, you will learn to add (combine) and subtract (take away) numbers up to 100. These are the two most important operations in mathematics — you will use them every single day!

Learning Objectives

  

• Add two numbers with sums up to 100

  

• Subtract numbers up to 100

  

• Use the column method (vertical addition/subtraction)

  

• Understand carrying (regrouping) in addition

  

• Understand borrowing in subtraction

  

• Solve simple word problems

1. Addition: Combining Numbers

Addition means putting numbers together to find the total (or sum).

The symbol for addition is + (plus). The answer is called the sum.

Example: 23 + 14 = ?

  

• Ones: 3 + 4 = 7

  

• Tens: 2 + 1 = 3

  

• Answer: 37

2. Column Addition (Vertical Method)

Write the numbers one above the other, lining up ones under ones and tens under tens:

  4 5
+ 3 2
------
  7 7

Step 1: Add the ones column: 5 + 2 = 7

Step 2: Add the tens column: 4 + 3 = 7

Answer: 77

3. Carrying (Regrouping)

What happens when the ones add up to 10 or more?

Example: 38 + 25 = ?

  ¹
  3 8
+ 2 5
------
  6 3

Step 1: Ones: 8 + 5 = 13. Write 3, carry 1 to the tens column.

Step 2: Tens: 3 + 2 + 1 (carried) = 6

Answer: 63

Rule: When a column adds up to 10 or more, write the ones digit and carry the tens digit to the next column.

4. Subtraction: Taking Away

Subtraction means taking one number away from another to find the difference.

The symbol for subtraction is − (minus). The answer is called the difference.

Example: 47 − 23 = ?

  4 7
− 2 3
------
  2 4

Step 1: Ones: 7 − 3 = 4

Step 2: Tens: 4 − 2 = 2

Answer: 24

5. Borrowing in Subtraction

What if the top digit is smaller than the bottom digit?

Example: 52 − 28 = ?

  ⁴ ¹²
  5 2
− 2 8
-------
  2 4

Step 1: Ones: 2 − 8 → cannot do! Borrow 1 ten from the 5 (becomes 4). The 2 becomes 12.

Step 2: 12 − 8 = 4

Step 3: Tens: 4 − 2 = 2

Answer: 24

Rule: When the top digit is too small, borrow 1 from the next column. That 1 becomes 10 in the current column.

6. Word Problems

Problem 1: Chisomo has 34 mangoes. She buys 28 more. How many mangoes does she have now?

Solution: 34 + 28 = 62 mangoes

Problem 2: A bus had 56 passengers. At the first stop, 19 got off. How many passengers remain?

Solution: 56 − 19 = 37 passengers

📝 Practice Exercises

  

1. 45 + 32 = ___

  

2. 67 + 28 = ___ (remember to carry!)
  
3. 83 − 41 = ___

  

4. 72 − 35 = ___ (remember to borrow!)

  

5. Thoko had 45 kwacha. She spent 28 kwacha on sweets. How much does she have left?

  

6. A farmer harvested 56 bags of maize in January and 37 bags in February. How many bags in total?

🎯 Key Takeaways

  

• Addition combines numbers; subtraction takes away

  

• Always line up ones under ones, tens under tens

  

• Carry when a column reaches 10 or more

  

• Borrow when the top digit is too small

  

• Word problems: look for keywords like "total" (add) or "left/remain" (subtract)

Next lesson: Multiplication Tables (1–12) — the shortcut for repeated addition!