The key to effective estimation is the ability to round mentally. This is a prerequisite skill for all estimation. This quick administered quick scored exercise is a perfect way to assess and/or help students understand the simplicity.
They are to each number to the "front-end place". That is a mathematical term for the highest place-value place.
No pencil calculation should be necessary, easy-to-cut answer templates are provided, as well as a quick-score quiz.
Please check out all of my worksheets. Most are very affordable, and very effective in intermediate student learning of mathematics.