Add a 1-digit number to a 2-digit number without regrouping

This understanding involves combining a two-digit number (10–99) with a one-digit number (0–9) when the ones digits total less than 10, so the ones are combined while the tens value remains unchanged. Place-value representations and number-line reasoning show why no exchange of 10 ones for 1 ten is needed, establishing a foundation for multi-digit addition; cases requiring regrouping or larger, more general addends are outside this scope.

Detailed Explanation: Add a 1-digit number to a 2-digit number without regrouping

To add a 1-digit number to a 2-digit number, add the ones first. If the ones total is less than $10$ , the tens stay the same.

Example: $34+5$

Break apart $34$ into $3$ tens and $4$ ones.
Add the ones:

4+5=9

The ones total is $9$ , which is less than $10$ . So, no new ten is needed.
Keep the $3$ tens and use the $9$ ones:

34+5=39

So, $\boxed{34+5=39}$ .

Learn by doing: Add a 1-digit number to a 2-digit number without regrouping

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Addition - Whole Number 2 digit + 1 digit, No Carry

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