National STEM Standards
STEM.M. MATHEMATICS: National Council of Teachers of Mathematics (NCTM)
NCTM.1. Number and Operations
1.3. Compute fluently and make reasonable estimates.
1.3.1. Select appropriate methods and tools for computing with fractions and decimals from among mental computation, estimation, calculators or computers, and paper and pencil, depending on the situation, and apply the selected methods.
1.3.3. Develop and use strategies to estimate the results of rational-number computations and judge the reasonableness of the results.