RemeliaMaths Year 4 Addition & subtraction
Year 4 column addition and subtraction
The objective: Add and subtract numbers with up to 4 digits using formal columnar methods.
The explanation, example and questions are the ones Remelia uses in the app; the questions are not taken from any test paper.
The idea
Column method with 4 digits works exactly as with 3: line up the place values and work right to left.
How to do it
- Write the numbers with ones under ones.
- Work right to left.
- Exchange when a column makes 10 or more, and when the top digit is too small.
A worked example
4,002 − 1,348 = 2,654. Check by adding: 2,654 + 1,348 = 4,002.
Watch for
Subtracting across a zero. In 4,002 − 1,348 you exchange from the thousands, turning the middle digits into 9s.
Try four questions
-
6,310 + 5,746 = ?
Show the answer to question 1
Answer: 12,056
Why:
Column method, ones first. When a column comes to 10 or more, exchange 10 for 1 in the next column.
-
Kai says: 9,556 − 583 = 9,033.
Is Kai right? Write the correct answer, not just yes or no.
Show the answer to question 2
Answer: 8,973 · "No, 8,973" is right too; "No" on its own scores nothing
Why:
Column method, ones first. Exchange from the next column when you cannot subtract.
Kai's answer was not right: the correct answer is 8973.
-
7,491 + 4,936 = ?
Round each number to the nearest hundred, then add. Which is the estimate?
- A 12,300
- B 12,400
- C 12,200
- D 12,100
Show the answer to question 3
Answer: B · 12,400
Why:
7,491 rounds to 7,500 and 4,936 to 4,900.
7,500 + 4,900 = 12,400. (The exact answer is 12,427.)
-
One digit is hidden under the box.
3,554 − 75□ makes 2,802
What is the hidden digit?
- A 2
- B 5
- C 3
- D 0
Show the answer to question 4
Answer: A · 2
Why:
3,554 − 752 = 2,802, so the hidden digit is 2.
Answers
- 1. 12,056
- 2. 8,973 · "No, 8,973" is right too; "No" on its own scores nothing
- 3. B · 12,400
- 4. A · 2
The mistakes Remelia names
When a wrong answer to a question like these matches one of these mistakes, the app says what the child seems to have done before they try again.
- Question 1, the answer 11,056: It looks as if a column came to 10 or more and nothing was exchanged. Write its ones digit, and exchange the ten for 1 in the next column to the left.
- Question 2, the answer 9,033: It looks as if you took the smaller digit from the bigger one, even where the bigger one was at the bottom. Where the top digit is smaller, exchange first: take 1 from the next column to the left, which makes 10 more in this one, then subtract.