Overview
This lecture explains how to add multi-digit numbers step-by-step, including aligning digits, adding columns, and handling carrying (re-grouping).
Understanding Multi-Digit Numbers
- A multi-digit number has more than one digit (e.g., 32, 215).
- Each digit in a number has a place value (ones, tens, hundreds, etc.).
Setting Up Addition Problems
- Stack numbers vertically so their digits in each place value are aligned.
- Always make sure the ones places are directly over each other.
- Draw a line under the bottom number and put a plus sign to the left.
Adding the Columns
- Begin adding from the rightmost column (ones place) and move left.
- Write the sum for each column below the line in the answer row.
Carrying (Re-grouping) in Addition
- If a column sum is two digits, write the rightmost digit in the answer and carry the left digit to the next column.
- Carrying means adding the extra digit to the top of the next column before summing.
Example Problems
- When adding 215 + 32, align and add each column, carrying only if needed.
- For 1,850 + 354, carry over when the sum in a column is 10 or more.
- When adding three numbers (e.g., 145 + 809 + 77), align all digits and carry as needed.
Practice and Checking Answers
- Practice regularly to master multi-digit addition.
- Use calculators to check answers and catch mistakes.
Key Terms & Definitions
- Multi-digit number — A number with more than one digit.
- Place value — The value of a digit based on its position (ones, tens, hundreds).
- Carrying (Re-grouping) — Moving a digit to the next column when the sum in a column is 10 or greater.
- Stacking — Writing numbers in a column, aligning place values for addition.
Action Items / Next Steps
- Complete the printable exercises for multi-digit addition.
- Check answers with a calculator for accuracy.
- Practice a few problems daily to reinforce skills.