X Tables
Place Value

Regrouping hundreds tens and ones

Model exchanging across multiple columns for addition and subtraction.

Quick answer

Regrouping hundreds, tens, and ones means exchanging between place value columns when adding or subtracting. For example, when you have 10 ones, you can exchange them for 1 ten. When you have 10 tens, you can exchange them for 1 hundred.

Learning outcome

By the end of this page, you will understand how to regroup hundreds, tens, and ones when adding and subtracting numbers, so you can solve bigger maths problems with confidence. Success signs:
  • You can explain what happens when you have 10 ones, 10 tens, or 10 hundreds
  • You can show how to exchange between columns when adding or subtracting
  • You can solve 3-digit addition and subtraction problems using regrouping
  • You can use base-10 blocks or drawings to show your work

Why this matters

Regrouping is an important skill because it helps you solve bigger maths problems that involve numbers over 100. You'll use this skill when:
  • Adding your pocket money from different weeks
  • Calculating how many steps you've walked in a day
  • Sharing a large number of toys or snacks
  • Measuring ingredients for a big cake
  • Playing games that involve counting scores or points
When you understand regrouping, you're building a strong foundation for more advanced maths like multiplication and division. It's like learning how to use the right tools for the job!

How it works

Regrouping is about exchanging between place value columns. Each column has a special value:
  • Ones column = 1
  • Tens column = 10
  • Hundreds column = 100
When you have 10 or more in any column, you can exchange them for the next bigger column:
  • 10 ten
  • 10 tens = 1 hundred
  • 10 hundreds = 1 thousand
The process works like this:
  1. Line up your numbers by place value (ones under ones, tens under tens, hundreds under hundreds)
  2. Add or subtract starting from the ones column
  3. If you have 10 or more in any column, exchange them for the next bigger column
  4. If you need to subtract but don't have enough in a column, borrow from the next bigger column

Examples you can see

Let's look at an addition problem: 247 + 186 Step 1: Line up the numbers by place value
HundredsTensOnes
247
186
Step 2: Add the ones column 7 + 6 = 13 ones We have 13 ones, which is 10 ones + 3 ones Exchange 10 ones for 1 ten So we write 3 in the ones column and carry 1 to the tens column Step 3: Add the tens column (including the carried 1) 4 + 8 + 1 = 13 tens We have 13 tens, which is 10 tens + 3 tens Exchange 10 tens for 1 hundred So we write 3 in the tens column and carry 1 to the hundreds column Step 4: Add the hundreds column (including the carried 1) 2 + 1 + 1 = 4 hundreds We have 4 hundreds, which is less than 10 So we write 4 in the hundreds column Final answer: 433 Let's try a subtraction problem: 321 - 157 Step 1: Line up the numbers by place value
HundredsTensOnes
321
157
Step 2: Subtract the ones column We can't take 7 from 1, so we need to borrow Borrow 1 ten from the tens column (2 tens becomes 1 ten) Add 10 ones to the ones column (1 + 10 = 11 ones) Now we can do 11 - 7 = 4 ones Step 3: Subtract the tens column (now 1 ten) We can't take 5 from 1, so we need to borrow Borrow 1 hundred from the hundreds column (3 hundreds becomes 2 hundreds) Add 10 tens to the tens column (1 + 10 = 11 tens) Now we can do 11 - 5 = 6 tens Step 4: Subtract the hundreds column 2 - 1 = 1 hundred Final answer: 164

Try it as a mini adventure

The Great Toy Swap Adventure You're planning a big toy swap with your friends. You have 247 toy cars, and your friend brings 186 toy cars. How many toy cars do you have altogether? Challenge: Solve this using regrouping. Step 1: Write down the numbers 247 cars + 186 cars = ? Step 2: Add the ones column 7 + 6 = 13 ones Exchange 10 ones for 1 ten Write down 3 ones and carry 1 ten Step 3: Add the tens column (including the carried 1) 4 + 8 + 1 = 13 tens Exchange 10 tens for 1 hundred Write down 3 tens and carry 1 hundred Step 4: Add the hundreds column (including the carried 1) 2 + 1 + 1 = 4 hundreds Step 5: Your final answer is 433 toy cars! Real-world tip: You can use base-10 blocks or draw pictures to help you visualize the regrouping. Try making 247 with blocks, then add 186 more. Count how many you have in total!

Common mistakes

  • Mistake: Forgetting to carry numbers when adding Why it happens: Kids get excited about adding and forget to write down the carried number Fix: Always put a small number above the column when you carry, and check it's in your final answer
  • Mistake: Borrowing from the wrong column when subtracting Why it happens: Confusion about which column to borrow from Fix: Always borrow from the column that has the bigger number, and make sure to reduce that column by 1
  • Mistake: Not exchanging properly between columns Why it happens: Not understanding that 10 ten, 10 tens = 1 hundred Fix: Practice with base-10 blocks or drawings to see the exchanges clearly
  • Mistake: Adding or subtracting in the wrong order Why it happens: Not lining up the numbers properly Fix: Always make sure ones are under ones, tens under tens, hundreds under hundreds

Parent and carer guide

Here's how you can help your child learn regrouping in just 5-10 minutes: What to say:
  • "Let's look at how many tens and ones we have"
  • "What happens when we have 10 ones? We can trade them for 1 ten"
  • "Can you show me with your blocks?"
  • "Let's think about which column we need to borrow from"
What to watch for:
  • Does your child line up numbers correctly?
  • Do they remember to carry numbers when adding?
  • Can they explain what they're doing?
  • Do they understand why we exchange between columns?
How to help:
  • Use base-10 blocks or drawings to show exchanges
  • Practice with real objects like coins or counters
  • Ask your child to explain their thinking
  • Play games where you add or subtract with 3-digit numbers
  • Don't rush - let them make mistakes and learn from them
What not to worry about:
  • Your child might get confused at first - that's normal
  • They might make small mistakes - these help them learn
  • They might want to use fingers instead of regrouping - that's okay for now

Practice questions

  1. What is 345 + 278? Answer: 623
  2. What is 512 - 287? Answer: 225
  3. What is 199 + 201? Answer: 400
  4. What is 700 - 345? Answer: 355
  5. What is 467 + 389? Answer: 856

FAQ

What does regrouping mean in maths?

Regrouping means exchanging between place value columns when adding or subtracting. For example, when you have 10 ones, you can exchange them for 1 ten. When you have 10 tens, you can exchange them for 1 hundred.

Why do we need to regroup?

We need to regroup because when we add or subtract, we might end up with more than 9 in any column. Since each column can only hold 0-9, we have to exchange the extra for the next bigger column to keep our numbers correct.

How do I know when to regroup?

You need to regroup when you have 10 or more in any column. For addition, you exchange the 10 for the next bigger column. For subtraction, you borrow from the next bigger column when you don't have enough in the current column.

Can I use base-10 blocks to help me?

Yes! Base-10 blocks are perfect for showing how regrouping works. You can use small cubes for ones, rods for tens, and flats for hundreds. This makes the exchanges visible and easier to understand.

What happens when I have 10 hundreds?

If you have 10 hundreds, you can exchange them for 1 thousand. This is the same pattern as ones to tens, and tens to hundreds. Each time, you're exchanging 10 of one column for 1 of the next bigger column.