When it’s too hard to count ’em up and too much time to calculate, it’s time to guesstimate the answer. I use this technique all the time to “ball park” my answer so I know if I’ve made a mistake with my final answer.
Download the student worksheet that goes with this lesson.
This lesson is useful when you don’t need an exact answer, or if the numbers are way too long to remember. It’s really pretty simple to do: you round up or down, and the closer to the ones digit you can handle, the more exact your answer will be.