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subtraction

Subtracting multiples of 10

Use tens structure to subtract 10, 20 or 30 mentally.

Quick answer

You can subtract multiples of 10 by counting back in tens, using a number line, or by thinking about how many tens you need to take away.

Learning outcome

By the end of this page, you will be able to subtract 10, 20, or 30 from any number up to 100 using mental maths strategies. Success signs:
  • You can quickly take away 10, 20, or 30 from a number in your head
  • You can use a number line to show how to subtract multiples of 10
  • You can explain how subtracting tens works using objects or drawings
  • You can solve word problems involving subtracting multiples of 10

Why this matters

Subtracting multiples of 10 is a super helpful skill that you use every day! When you're sharing sweets with friends, counting money, or even playing games, you often need to take away groups of 10. This skill helps you do maths quickly and easily without needing to write everything down. It's also the foundation for bigger subtraction problems and helps you understand how numbers work together.

How it works

Subtracting multiples of 10 is like taking away groups of 10. If you have 50 sweets and you eat 20, you're taking away 2 groups of 10. You can do this in your head by thinking:
  • 50 - 10 = 40
  • 40 - 10 = 30
So 50 - 20 = 30. You can also think of it as moving backwards on a number line. If you start at 50 and move back 20 spaces (2 groups of 10), you land on 30.

Examples you can see

Let's look at some examples using different methods: Example 1: Counting back in tens
  • 70 - 30 = ?
  • Start at 70, count back 30: 70, 60, 50, 40
  • So 70 - 30 = 40
Example 2: Using a number line
  • 60 - 20 = ?
  • Draw a line from 60 to 40
  • Move back 2 groups of 10
  • 60 - 20 = 40
Example 3: Using objects
  • You have 80 marbles
  • You give 30 to your friend
  • Count out 30 marbles and put them aside
  • Count the remaining marbles: 50
  • So 80 - 30 = 50
Example 4: Using patterns
  • When you subtract 10 from any number, the tens digit goes down by 1
  • When you subtract 20, the tens digit goes down by 2
  • When you subtract 30, the tens digit goes down by 3
  • So 90 - 30 = 60 because 9 tens minus 3 tens = 6 tens

Try it as a mini adventure

The Treasure Hunt Challenge You're going on a treasure hunt! Your map shows you have 90 coins to start with. Here's your journey: 1st time: You find a chest with 10 coins inside. How many coins do you have now? 2nd time: You spend 20 coins on a magic potion. How many coins do you have now? 3rd time: You find a second chest with 30 more coins. How many coins do you have now? 4th time: You give 10 coins to a friendly dragon. How many coins do you have now? Answer: 1st time: 90 + 10 = 100 coins 2nd time: 100 - 20 = 80 coins 3rd time: 80 + 30 = 110 coins 4th time: 110 - 10 = 100 coins You end up with 100 coins!

Common mistakes

  • Mistake: Thinking 50 - 30 = 20 because you only subtract the 3 from the 5
    Why it happens: Confusing the process of subtracting tens with subtracting ones
    Fix: Remember that 30 means 3 groups of 10, so count back 3 groups of 10 from 50
  • Mistake: Adding instead of subtracting when seeing "minus" in a word problem
    Why it happens: Not reading the problem carefully or confusing the meaning of words
    Fix: Read the problem twice and look for words like "take away", "left", "how many more", or "difference"
  • Mistake: Forgetting to change the tens digit when subtracting multiples of 10
    Why it happens: Not understanding that subtracting tens changes how many tens you have
    Fix: Use the pattern rule: if you subtract 10, the tens digit decreases by 1
  • Mistake: Counting backwards incorrectly on a number line
    Why it happens: Miscounting or not moving the right number of steps
    Fix: Count each step carefully or use a marker to show where you land

Parent and carer guide

To help your child practice subtracting multiples of 10, try these 5-10 minute activities:
  • Play "Subtract the Tens" game: Use 100 counters or coins. Start with 60, then subtract 10, 20, 30, etc. Count how many you have left each time
  • Use the number line: Draw a line from 0 to 100. Have your child jump back 10, 20, or 30 spaces for different subtractions
  • Practice with everyday objects: Count out 50 pasta pieces, take away 20, count how many are left
  • Ask your child to explain how they solved a problem: "How did you figure out 70 - 30?" This builds confidence and understanding
  • Make it fun: Create a story where your child is a treasure hunter, a shopkeeper, or a teacher counting students
Remember: Don't worry if your child makes mistakes! These are learning opportunities. Focus on understanding the process, not just getting the right answer.

Practice questions

  1. What is 80 - 20?
  2. Subtract 30 from 90.
  3. How much is 60 - 10?
  4. Take away 40 from 70.
  5. What is 100 - 30?
  6. Subtract 20 from 50.
  7. How much is 90 - 40?
  8. What is 30 - 10?
  9. Take away 50 from 80.
  10. Subtract 30 from 100.
Answers:
  1. 60
  2. 60
  3. 50
  4. 30
  5. 70
  6. 30
  7. 50
  8. 20
  9. 30
  10. 70

FAQ

What does "multiples of 10" mean?

Multiples of 10 are numbers that come in groups of 10: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, and so on.

Why is it easier to subtract multiples of 10?

Because you only need to change the tens digit, not the ones digit. This makes it much faster than subtracting numbers like 17 or 23.

Can I use this method with bigger numbers?

Yes! Once you understand this pattern, you can use it with numbers up to 1000. For example, 500 - 200 = 300.

How can I practice this at home?

Use everyday situations like counting money, sharing snacks, or playing games where you need to take away groups of 10.

What if I need to subtract a number that's not a multiple of 10?

Break it down into multiples of 10. For example, to subtract 27, you can subtract 20 then 7. But for now, focus on subtracting multiples of 10 first!