Number & Operations in Base Ten
Adding Two-Digit Numbers
Adding up to four two-digit numbers using place-value strategies.
Adding Several Two-Digit Numbers
Adding two numbers together is familiar by now. This lesson extends that skill to adding up to four two-digit numbers at once, using the same place-value thinking to keep everything organized.
The key strategy is to add the ones digits together first, then add the tens digits together, and finally combine those two results. If the ones digits add up to 10 or more, that extra ten gets bundled in with the tens.
Worked Example — Adding Three Two-Digit Numbers
Worked Example — Adding Four Two-Digit Numbers
Tip
Common Mistakes
Forgetting to carry an extra ten into the tens column when the ones digits add up to 10 or more.
Whenever the ones digits sum to 10 or more, write down the ones part and add the tens part into the tens column before finishing.
Adding tens digits and ones digits together in the same step, mixing up the two place values.
Keep the ones column and tens column completely separate until each one has been fully added, then combine the two totals at the end.
Key Takeaways
- Adding several two-digit numbers means adding the ones digits together and the tens digits together separately.
- A ones-column sum of 10 or more creates an extra ten that carries into the tens column.
- Keeping ones and tens separate until the end avoids place-value mistakes.
Summary
Adding several two-digit numbers at once uses place value to stay organized. The final lesson in this unit extends addition and subtraction one step further, into full three-digit numbers.
Sign in to track your progress and mark this lesson complete.
Track your progress