🔢 Addition & Subtraction (Large Numbers)
Line up place values; work from the right
▶ Play Door 3Adding & Subtracting Large Numbers
Add and subtract large numbers the same way as small ones — line up the place values and work from the right, carrying (in addition) or borrowing (in subtraction) when needed.
Example: 3,456 + 2,789 → add ones, tens, hundreds, thousands, carrying each time, to get 6,245.
Worked example
Problem: Add 3,456 + 2,789.
- Carry through each column: 6,245.
Answer: Carry through each column: 6,245.
Estimating & Word Problems
Estimating means rounding first to get a quick, close answer. Round each number to the nearest 100 or 1000, then add or subtract.
In word problems, total / altogether / in all mean add; left / difference / how many more mean subtract. You can check your exact answer against your estimate.
Worked example
Problem: Estimate 298 + 503 by rounding to the nearest 100.
- 300 + 500 = 800 (exact is 801).
Answer: 300 + 500 = 800 (exact is 801).