With a student who completes the following problem like this, 320+50=820, I might first recognize to myself (internally) that this student is needing support with recognizing place value in the problem. I would then prompt the student to walk me through the strategies and thinking they used to solve the problem. If they can recognize their own mistake, I might engage them in a conversation regarding how they might fix it. If they are unable to recognize their mistake or if they aren’t sure how to fix their mistake, I might have the student solve the problem using a place value or HTO chart and base-10 blocks.
