Lesson: Adding with Regrouping

Introduction

In this lesson, we will learn how to add numbers that require regrouping (or carrying). This occurs when the sum of a column exceeds 9, requiring us to carry over to the next column.

Steps to Add with Regrouping

1. Align the Numbers: Write the numbers one under the other, aligning the digits by place value (ones, tens, hundreds, etc.).
2. Start from the Right: Begin adding from the rightmost column (ones).
3. Regroup if Necessary: If the sum of a column is 10 or more, carry over the extra value to the next column on the left.
4. Continue Adding: Proceed to add the next column, including any carried value.
5. Write the Final Sum: Write the result below the line.

Example

Let's add 27 and 58:

1. Align the numbers:

   $$\begin{array}{rr} & 2 & 7 \\ + & 5 & 8 \\ \end{array}$$

2. Start with the ones column: $7 + 8 = 15$. Write down 5 and carry over 1.

3. Next, add the tens column: $2 + 5 + 1 = 8$. Write down 8.

4. The final result is:

   $$\begin{array}{rr} & 2 & 7 \\ + & 5 & 8 \\ \hline & 8 & 5 \ \end{array}$$

Thus, $27 + 58 = 85$.

Key Questions

• What do you do when the sum of a column is 10 or more?
• How do you know where to write the carried number?
• Can you give another example of addition that requires regrouping?

Keywords

• Regrouping
• Carrying
• Addition
• Place Value
• Sum