U.S. National Standards
N.1. Number and Operations (NCTM)
1.3. Compute fluently and make reasonable estimates.
1.3.2. Develop fluency in adding, subtracting, multiplying, and dividing whole numbers.
1.3.6. Select appropriate methods and tools for computing with whole numbers from among mental computation, estimation, calculators, and paper and pencil according to the context and nature of the computation and use the selected method or tools.
N.2. Algebra (NCTM)
2.3. Use mathematical models to represent and understand quantitative relationships.
2.3.1. Model problem situations with objects and use representations such as graphs, tables, and equations to draw conclusions.