ADDITION & SUBTRACTION · TEXTBOOK LESSON
Addition combines quantities to find a total. Efficient addition depends on number bonds, place value and the fact that numbers can often be regrouped to make friendlier calculations.
Learning objectives
By the end of this lesson, you should be able to:
- Interpret + and = correctly.
- Recall and use number bonds.
- Add mentally by making 10, partitioning or using doubles.
- Use column addition when place value requires a written method.
- Check addition with estimation or subtraction.
1. Key vocabulary and definition
Definition
If a and b are addends, their sum is written a + b. Addition is commutative: a + b = b + a. It is also associative: (a + b) + c = a + (b + c).
addendsumtotalnumber bondcommutativeplace value
2. Essential facts and rules
These are the facts you should know before attempting the worked example.
Key mathematical facts
- Number bonds to 10 include 0+10, 1+9, 2+8, 3+7, 4+6 and 5+5.
- Making the next multiple of 10 can simplify mental addition.
- In column addition, digits must be aligned by place value.
3. Standard method
A reliable method helps prevent errors and makes your reasoning easy to follow.
1
Decide whether a mental or written method is most efficient.
2
For mental addition, partition one number or bridge through 10.
3
For column addition, line up ones, tens, hundreds and so on.
4
Add from right to left, regrouping when a place-value total is 10 or more.
5
Check using subtraction or an estimate.
4. Worked example
Worked example
Calculate 38 + 27.
1
Partition 27 into 20 + 7.
2
Add the tens: 38 + 20 = 58.
3
Add the ones by bridging through 60: 58 + 2 = 60, then +5 = 65.
4
Check: 65 - 27 = 38, so the addition is correct.
5. Common mistakes
Watch out for these
- Adding digits without respecting place value.
- Forgetting to regroup when a column totals 10 or more.
- Treating the equals sign as 'the answer comes next' instead of 'has the same value as'.
6. Video lesson
Watch the lesson, pause when needed, and reproduce the examples on paper rather than only watching passively.
7. Practice exercise
Complete these without looking at the answers first.
- Calculate 7 + 8.
- Calculate 19 + 6 using a make-20 strategy.
- Calculate 46 + 37.
- Find the missing number: 28 + □ = 50.
- A class has 24 pupils and 18 visitors. How many people are there altogether?
Show answers
- 15
- 25
- 83
- 22
- 42 people
8. Chapter summary
- Addition finds a combined total.
- Use number bonds and place value to choose an efficient strategy.
- Addition can be checked using subtraction.