Column Addition Experts: Tackling Mixed Digits with Carrying!

Hello Mighty Maths Solvers! You’re becoming fantastic at column addition. Now it’s time for a super challenge: adding a 3-digit number and a 2-digit number together when we need to do some carrying (or regrouping)! This means that sometimes when we add a column, we’ll have too many for that column, and we’ll need to carry over to the next one. Don’t worry, we’ll break it down step-by-step!

The Golden Rules: Alignment and Carrying!

Remember, even with carrying, the first golden rule is alignment:

• Ones go under Ones.
• Tens go under Tens.
• Hundreds go under Hundreds (the 2-digit number won’t have a hundreds digit, so that space under the 3-digit number’s hundred will be empty or a zero).

The second golden rule is knowing when and how to carry.

Let’s Add with Carrying: Example 347 + 85

Here’s how we set it up and solve it:

Step 1: Write the numbers one above the other, aligning them perfectly.

  H T O  (H for Hundreds, T for Tens, O for Ones)
  3 4 7
+   8 5  (Notice the empty space in the hundreds column for 85)
-------  (Draw a line underneath for your answer)

Step 2: Add the Ones Column First – and Carry if Needed! Look at the ‘Ones’ (O) column: 7 + 5. 7 + 5 = 12. This is 1 ten and 2 ones. We write the 2 ones under the ones column. We “carry” the 1 ten over to the top of the tens column.

  (¹)    <-- Carried 1 ten
  H T O
  3 4 7
+   8 5
-------
      2

Step 3: Add the Tens Column Next – Including the Carried Ten! Now look at the ‘Tens’ (T) column. We have the 1 ten we carried, plus 4 tens, plus 8 tens. So, we add: 1 + 4 + 8 = 13 tens. Wow! 13 tens is actually 1 hundred and 3 tens. So, we write the 3 tens under the tens column. And we “carry” the 1 hundred over to the top of the hundreds column.

(¹) (¹)  <-- Carried 1 hundred, Carried 1 ten
  H T O
  3 4 7
+   8 5
-------
    3 2

Step 4: Add the Hundreds Column – Including Any Carried Hundred! Finally, look at the ‘Hundreds’ (H) column. We have the 1 hundred we carried, plus the 3 hundreds from 347. The number 85 has no hundreds digit (or it’s a 0). So, 1 + 3 + 0 = 4 hundreds. Write the answer (4) directly below the hundreds column.

(¹) (¹)
  H T O
  3 4 7
+   8 5
-------
  4 3 2

So, 347 + 85 = 432! You handled carrying in two places!

Sometimes you might only need to carry from the ones to the tens, or just from the tens to the hundreds (if the ones didn’t need carrying but the tens did). Always check each column!

Practice Your Carrying with Mixed Digits! (18 Questions)

Ready to show off your expert column addition? Here are 18 questions where you’ll add a 3-digit number and a 2-digit number, and you’ll likely need to do some carrying. Line them up, add column by column (starting with ones!), and don’t forget to add any numbers you carry!

(Your web app with the 18 questions will go here. The app should ideally support clear columnar layout and indication of carried digits.)

Why is Mastering This Column Addition So Important?

• Handles Most Addition: This skill lets you add almost any set of whole numbers accurately.
• Deepens Place Value Knowledge: You really see how ones, tens, and hundreds regroup and exchange.
• Essential for Future Maths: It’s a building block for multiplication, subtraction with borrowing, and much more.
• Builds Major Maths Confidence: Being able to solve these sums correctly is a fantastic achievement!

Guidance for Grown-Ups: Supporting Complex Carrying

Adding a 3-digit and a 2-digit number with regrouping requires careful attention to alignment and understanding the carrying process across multiple columns if necessary.

• Solidify Alignment: Continue to use H T O headings and squared paper if it helps ensure the 2-digit number is correctly placed under the 3-digit number.
• One Column at a Time: Emphasise working strictly from right to left: ones, then tens, then hundreds.
• Clearly Mark Carried Digits: Encourage a consistent way to note carried digits (e.g., small and above the next column to the left).
• Talk Through “Double Carries”: For sums like the example (347+85), where carrying happens from ones-to-tens AND tens-to-hundreds, explicitly walk through each step.
• Use Base-Ten Blocks: If a child is struggling with the concept of regrouping 10 tens as 1 hundred, using base-ten blocks to model the exchange can be very powerful.