Skill: Add a 1-digit number to a 2-digit number with regrouping

Explanation and Free Practice Resources

This understanding involves adding a one-digit addend to a two-digit number when the ones combine to make 10 or more, composing a new ten and representing the result through place value: for example, 27 + 6 becomes 3 tens and 3 ones, or 33. It connects concrete, visual, and written forms of regrouping while preventing the misconception that digits can be added independently; larger numbers and more advanced multi-digit cases are not included.

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Detailed Explanation: Add a 1-digit number to a 2-digit number with regrouping

When adding a 1-digit number to a 2-digit number, start with the ones. If the ones make $10$ or more, regroup $10$ ones as $1$ new ten.

Example: $27+6$

Break $27$ into $2$ tens and $7$ ones:

27=2\text{ tens }+7\text{ ones}

Add the $6$ ones:

7\text{ ones}+6\text{ ones}=13\text{ ones}

Regroup $13$ ones as $1$ ten and $3$ ones:

13\text{ ones}=1\text{ ten}+3\text{ ones}

Add the tens. The original $2$ tens plus the new $1$ ten make $3$ tens. There are $3$ ones left:

3\text{ tens}+3\text{ ones}=33

So,

\boxed{27+6=33}

Remember: combine the ones first. When they make $10$ or more, trade $10$ ones for $1$ ten.

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Addition - Whole Number 2 digit + 1 digit, With Carry

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