Understanding this skill means interpreting each two-digit number as tens and ones, combining corresponding place values, and recognizing that ten or more ones can be composed as one additional ten. The learner connects place-value representations and written equations, explains why the regrouped ten is added to the tens, and maintains the value of the sum; the scope is limited to adding two two-digit whole numbers, including sums that may reach the hundreds, not larger or more generalized algorithms.
A two-digit number has tens and ones. Add the ones first, then the tens.
Example: Find .
Thirteen ones are the same as ten and ones. Write in the ones place and regroup ten.
The regrouped ten is added to the tens because ones have the same value as ten.
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