Skill 6J
Estimating Differences - Nearest ten
It is not always necessary to find the exact answer to a problem. Sometimes we only need to find an approximate answer.  Depending on the situation, your student may need to round to the nearest 1000 (thousands place), nearest 100 (hundreds place) or the nearest 10 (tens place).  Your student should do this by re-writing the problem in its "rounded" form, and then solve for the answer. Eventually, with enough practice, this type of problem can be done mentally without even being written.
Round the top and bottom number in the problem to the nearest ten.  Then subtract to estimate the difference.

646

= ?            

- 322

= ?