Adding two digit numbers can seem like an easy enough task to those of us who have been doing it for a long time! But for elementary students it can sometimes be confusing, especially if there is regrouping involved.
It is helpful to most students to start with something concrete, like place value blocks. Before I teach students the standard algorithm for adding two digit numbers, we spend time exploring with place value blocks. This leads into the partial sums strategy (also known as expanded form strategy). Below is a brief overview of starting the strategy using blocks.
Eventually the students will practice the strategy without the blocks and then we move into other addition strategies such as number lines and the algorithm.