Big Idea
Addition combines amounts; subtraction finds what is left or the difference between two amounts.
Addition and Subtraction
Add, subtract, estimate, and check answers accurately.
Understand it first
Column alignment
Digits must line up by place value: ones under ones, tens under tens.
Inverse checks
Addition and subtraction undo each other, so use one to check the other.
Estimating
Rounding first helps you notice answers that are much too big or small.
Method Ladder
Use this same ladder every time you meet this topic.
- Line up digits by place value.
- Start from the ones column.
- Carry or exchange when needed.
- Check with the inverse operation.
Worked example: Calculate 734 - 286
- Line up 734 and 286.
- In the ones column, exchange: 14 - 6 = 8.
- In the tens column, after exchange: 12 - 8 = 4.
- In the hundreds column: 6 - 2 = 4.
- Answer: 448. Check: 448 + 286 = 734.
Fix It Lab
Read these before the quiz. They are the traps that lose marks.
- Common mistakeNot lining up digits properly.
- Common mistakeForgetting to carry or exchange.
- Common mistakeSubtracting the smaller digit from the larger digit in each column instead of following the top number.
Top-mark challenge
Open challenge
A shop has 1,250 pencils and sells 486. How many are left?
Write full working and one sentence explaining the method.
10-question unlock quiz
The quiz is now on separate pages. You answer one question, then the next question opens. Finish Question 10 to complete this mission.
Start Question 1