Mental adjustment
4,320 + 300 = 4,620.
Only the hundreds change here.
Year 4
Add and subtract numbers with up to 4 digits using the formal written methods of columnar addition and subtraction where appropriate
Choose sensible mental or written strategies and keep the place values lined up when working with four-digit numbers.
Lesson overview
Number - addition and subtraction
Some calculations are quick to do mentally, especially when only one place value changes. Other calculations are better with a written method. The important part is choosing a method that fits the numbers and then keeping the place values clear.
Use column layout when needed
3,468 + 1,203 is easier when the thousands, hundreds, tens and ones are lined up.
Match each place value before calculating.
Subtraction with place value
6,500 - 2,000 = 4,500.
The thousands change and the hundreds stay the same.
Worked example
Work out 2,346 + 1,123.
- Line up the thousands, hundreds, tens and ones.
- Add the ones: 6 + 3 = 9.
- Add the tens: 4 tens + 2 tens = 6 tens. Add the hundreds: 3 hundreds + 1 hundred = 4 hundreds.
- Add the thousands: 2 thousands + 1 thousand = 3 thousands, so the total is 3,469.
Round 1: Learn it
Choose the calculation carefully and keep the place values clear.
Finish this round to unlock Round 2: Show you know it.
Question 1
4,560 + 200 =
Question 2
What is 3,421 + 1,200?
Question 3
What is 7,000 - 400?
Question 4
2,345 + 1,111 =
Question 5
Which answer is correct for 6,532 - 2,000?
Common mistakes
Watch for these as you work through the lesson.
- Changing the wrong place value in a mental calculation.
- Not lining up the digits by place value.
- Choosing a mental method when the written method would be clearer.
Related topics
These ideas connect closely to this lesson.
- Estimate and use inverse operations to check answers to a calculation.
- Solve addition and subtraction two-step problems in contexts, deciding which operations and methods to use and why.