Subtraction – Basic 1 Mathematics Lesson Note (Third Term)

Subtraction involving addition

Checking Subtraction with Addition: When we subtract, we can check our answer by adding.

Example: 9 – 4 = 5 Check: 5 + 4 = 9 ✓

Rule: If a – b = c, then c + b = a

Exercise 12: Subtract and check with addition:

1. 8 – 3 = ___ Check: ___ + 3 = 8
2. 10 – 6 = ___ Check: ___ + 6 = 10
3. 9 – 2 = ___ Check: ___ + 2 = 9
4. 7 – 4 = ___ Check: ___ + 4 = 7

Exercise 13: Complete the subtraction and addition:

1. 15 – 7 = ___ Check: ___ + 7 = 15
2. 12 – 5 = ___ Check: ___ + 5 = 12
3. 18 – 9 = ___ Check: ___ + 9 = 18

Exercise 14: Use addition to find the missing number:

1. 11 – ___ = 4 Think: 4 + ___ = 11
2. 16 – ___ = 8 Think: 8 + ___ = 16
3. 13 – ___ = 6 Think: 6 + ___ = 13

Exercise 15: Subtraction word problems with checking:

1. Tom had 14 apples. He ate 6 apples. How many apples are left? 14 – 6 = ___ Check: ___ + 6 = 14
2. There were 20 birds in the tree. 8 birds flew away. How many birds are left? 20 – 8 = ___ Check: ___ + 8 = 20
3. Mary had 17 stickers. She gave away 9 stickers. How many stickers does she have left? 17 – 9 = ___ Check: ___ + 9 = 17

Exercise 16: True or False? Check using addition:

1. 13 – 5 = 8 ___ Check: 8 + 5 = ___
2. 16 – 7 = 8 ___ Check: 8 + 7 = ___
3. 19 – 6 = 13 ___ Check: 13 + 6 = ___

Exercise 17: Complete the fact families:

1. 12 – 4 = 8 8 + 4 = ___ 4 + 8 = ___ 12 – 8 = ___
2. 15 – 6 = 9 9 + 6 = ___ 6 + 9 = ___ 15 – 9 = ___

Exercise 18: Find the missing numbers:

1. 🍎🍎🍎🍎🍎🍎🍎🍎🍎🍎 – 🍎🍎🍎🍎 = ___ Check: ___ + 4 = 10
2. ⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐⭐ – ⭐⭐⭐⭐⭐⭐⭐ = ___ Check: ___ + 7 = 15