The Common Core State Standards teach students the algorithm for multi-digit addition and subtraction in 4th grade. But some experts say it should be taught sooner.

If the bottom digit is larger than the top digit, they go to the 10s column to the left, and "borrow" a 10, adding 10 to the ones digit and subtracting 1 from the 10s digit.

Conceptually based instruction on place value and two-digit addition and subtraction without regrouping was provided in four first-grade classrooms, and more conventional textbook-based instruction ...

Students go over addition and subtraction with regrouping using different strategies.

Mental subtraction is easiest when you can subtract each digit without having to borrow from the next place up. If the second number has some bigger digits than the first, it gets more complicated.

This study examined Korean second and third graders' understanding of multidigit addition and subtraction and particularly their ability to explain the trading required when a column sum of the ...

Addition and subtraction with regrouping using different strategies to solve.