subtraction
Subtraction misconceptions
Fix common errors in regrouping, direction and word-problem interpretation.
Quick answer
Subtraction misconceptions happen when children think that subtraction always makes numbers smaller, that you always subtract the smaller number from the larger one, or that regrouping is just "borrowing" without understanding what's happening. These mistakes can be fixed with clear examples, hands-on practice, and good explanations.Learning outcome
By the end of this page, you will understand the most common mistakes when subtracting numbers and how to avoid them. Success signs:- You can explain why subtraction can sometimes make a number bigger
- You can solve subtraction problems with regrouping without just "borrowing" blindly
- You can read word problems and choose the correct subtraction operation
- You can check if your subtraction answer makes sense
Why this matters
Subtraction is one of the first operations children learn, but it can be tricky. When children misunderstand how subtraction works, they might get confused in later maths, like working with negative numbers or solving word problems. Understanding subtraction well helps you do better in school and in everyday life, like sharing snacks, saving money, or understanding time.How it works
Subtraction is about taking away or finding the difference between two numbers. It's like asking, "How much more is this than that?" or "How many are left?" Sometimes, children think subtraction always means making a number smaller, but that's not always true. Here are the steps to understand subtraction better:- Understand that subtraction is about comparing or taking away
- Realise that subtracting a smaller number from a larger one usually gives a smaller answer
- Learn that subtracting a negative number makes the answer bigger
- Understand regrouping (or borrowing) as a way to make subtraction easier
- Check your answer to make sure it makes sense
Examples you can see
Let's look at some real examples to understand how subtraction works. Example 1: Subtracting a smaller number from a larger one If you have 8 apples and eat 3, you have 8 - 3 = 5 apples left. This makes sense because you took away some apples. Example 2: Subtracting a negative number If you have 5 apples and someone takes away -3 apples (which means they give you 3 apples), you now have 5 - (-3) = 8 apples. This makes the number bigger because you're adding more apples. Example 3: Regrouping in subtraction When subtracting 27 - 19, you might need to regroup:- Start with 27 (2 tens and 7 ones)
- Since 7 is less than 9, you take one ten (making 1 ten and 17 ones)
- Now subtract 9 from 17 ones
- Subtract 1 from 1 ten = 0 tens
- Answer = 8
Try it as a mini adventure
Adventure: The Treasure Hunt You're going on a treasure hunt with your friends. You start with 20 coins in your backpack. You find a chest with 15 more coins, but then you give 8 coins to your friend to help them with a puzzle. How many coins do you have now?- Start with: 20 coins
- Find more: 20 + 15 = 35 coins
- Give away: 35 - 8 = ? coins
- Answer: 27 coins
Common mistakes
Here are some of the most common mistakes children make with subtraction and how to fix them. Mistake 1: Thinking subtraction always makes numbers smaller What happens: A child sees 5 - 3 = 2 and assumes that subtracting always makes things smaller. Why it happens: They only see examples where one number is bigger than the other. Fix: Show that subtracting a negative number makes the answer bigger. For example, 5 - (-3) = 8. Mistake 2: Confusing the order of numbers What happens: A child sees "There are 12 apples and 5 are eaten. How many are left?" and writes 5 - 12 = -7. Why it happens: They don't understand that the first number is the total and the second is what's taken away. Fix: Encourage children to read the question carefully and identify what's being taken away. Mistake 3: Not understanding regrouping What happens: A child tries to do 27 - 19 but doesn't know how to regroup, so they get confused. Why it happens: They don't understand the value of tens and ones. Fix: Use base-10 blocks or drawings to show how regrouping works. Mistake 4: Forgetting to check the answer What happens: A child answers 15 - 7 = 8, but doesn't check if it's right. Why it happens: They rush through the problem. Fix: Teach them to add the answer back to the number they subtracted to see if they get the original number.Parent and carer guide
Parents and carers can help children understand subtraction misconceptions by:- Using real-life examples like sharing food or counting toys
- Encouraging children to explain their thinking out loud
- Using visual aids like blocks, drawings, or counters
- Practicing word problems together to understand what is being asked
- Checking answers by adding the result back to the number subtracted
- Being patient and celebrating small improvements
Practice questions
- What is 10 - (-2)?
- Which is bigger: 15 - 8 or 15 - 12?
- Subtract 23 from 31 using regrouping.
- There were 25 children at the party. 17 children left. How many are left?
- What is 7 - 12?
- 12
- 15 - 8 (because 7 is bigger than 3)
- 8
- 8 children
- -5
FAQ
What is the difference between addition and subtraction?
Addition combines numbers to make a larger total, while subtraction takes away from a number to find a smaller amount or difference.
Why do we need to understand subtraction misconceptions?
Understanding these mistakes helps children avoid confusion, build confidence, and learn to solve problems correctly in maths and real life.
Can subtraction ever make a number bigger?
Yes, when you subtract a negative number, the result is bigger. For example, 5 - (-3) = 8.
How can I help my child with subtraction at home?
You can use everyday examples, practice word problems, use visual aids, and encourage your child to explain their thinking.
What should I do if my child keeps making the same subtraction mistake?
Revisit the concept with new examples, use different methods (like drawing or counting), and be patient. Practice regularly and celebrate progress.