Their study of mathematics should include specific instruction in ways to estimate, when it is appropriate to estimate, and how close an estimate is reasonable. Estimates are important when determining whether the result of a computation or the answer to a problem is reasonable. Frequently, an estimate is more appropriate than an exact answer.
Estimates are important both in computation and in measurement.
There is some overlap in the objectives included in this strand and in the measurement strand. A single lesson might include objectives from each of these strands. Practice in mental computation provides children an opportunity to explore different combinations of numbers and alternative strategies for working with numbers. It is an important incentive for internalizing work with manipulatives. A combination of estimations and mental computation helps children become more flexible in applying computation skills and better able to select a method of computation most appropriate for a given situation.