Addition (Core Skills)
Master the column method and regrouping (carrying) to add multi-digit numbers accurately — the foundation of every budget and total.
You add numbers constantly — grocery totals, hours worked, miles driven. But when you add multi-digit numbers incorrectly — especially when carrying — errors compound. A single missed carry can throw off an entire budget or invoice.
- Add multi-digit numbers using the column (vertical) method
- Apply regrouping (carrying) when a column sum reaches 10 or more
- Use addition to total expenses, hours, and quantities in real-world scenarios
Addition combines quantities to find a total. When using the column method, always start from the ones column (rightmost) and work left. If any column adds up to 10 or more, write the ones digit and carry the tens digit to the next column.
\[ \text{Addend} + \text{Addend} = \text{Sum} \]Column Addition Layout
Stack the numbers so each digit aligns with its place value column, then add column by column from right to left.
Example: 346 + 578 — step by step
| carry → | 1 | 1 | |
| 3 | 4 | 6 | |
| + | 5 | 7 | 8 |
| 9 | 2 | 4 | |
Calculate: \(45 + 27\)
- Ones: \(5 + 7 = 12\) → write 2, carry 1
- Tens: \(4 + 2 + 1 = 7\) → write 7
Calculate: \(346 + 578\)
- Ones: \(6 + 8 = 14\) → write 4, carry 1
- Tens: \(4 + 7 + 1 = 12\) → write 2, carry 1
- Hundreds: \(3 + 5 + 1 = 9\) → write 9
Your three biggest monthly expenses are: rent $1,250, car payment $387, groceries $428. What's the total?
- Add rent + car: \(1{,}250 + 387 = 1{,}637\)
- Add groceries: \(1{,}637 + 428 = 2{,}065\)
Your top three expenses total $2,065 per month.
Try these before moving on:
- Calculate: \(67 + 45\)
- Calculate: \(483 + 259\)
- You work 38 hours one week and 42 hours the next. What's your total?
▶ Show Answers
- 112 — ones: 7+5=12 (write 2, carry 1); tens: 6+4+1=11 (write 1, carry 1); hundreds: 1.
- 742 — ones: 3+9=12; tens: 8+5+1=14; hundreds: 4+2+1=7.
- 80 hours — 38 + 42 = 80.
- Forgetting to add the carry: After carrying a 1, you must add it to the next column. It's easy to skip — especially in the middle of a long problem.
- Misaligning columns: Each digit must sit under its matching place value. Ones under ones, tens under tens. Even one column off and your answer is completely wrong.
- Starting from the left: Always add from the right (ones first). Starting left means you'll need to go back and adjust anyway — addition runs right to left.
- Add right to left — start at the ones column and move left.
- Carry when a column hits 10 or more — write the ones digit, carry the tens digit.
- Column alignment is critical — misaligned digits produce wrong answers.
- Addition is commutative — 3 + 5 = 5 + 3. The order doesn't change the sum.
Bookkeepers total income and expense columns daily. Construction managers add material quantities across dozens of line items. A single missed carry in a purchase order or invoice can cascade into a significant budget discrepancy that takes hours to track down.
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Addition (Core Skills) — Quiz
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