Teachers call these: Bell Ringers, Do Now, Warm-Up, etc.
Establishing learning routines not only increases the effective use of instructional time, but also sets the tone for class to begin.
This article from Corwin Connect provides 6 reasons why this is a solid practice. It also offers some variety of purpose for the task. Is the intent to provide spaced practice? Build number sense? Strengthen thinking and reasoning? Being intentional with how these activities are selected can address additional skills beyond pre/post assessment for today's LT.
Use this link and click on "Get Your Complementary Math Tasks" for grade specific rich tasks you can use in your math classroom.
How does this connect to 5D? CEC2 Learning Routines