Students will solve one-step word problems involving "add to situations" with result unknown, change unknown and start unknown (within 100). Prior Knowledge Required: Familiarity with the common addition and subtraction situations from first grade; ability to identify the actions that occur in a problem; able to draw from a variety of strategies developed in first grade for solving problems, including an understanding of properties of operations for addition and subtraction; understand the meaning and process of measurement including the concept of iterating; be able to add and subtract; prior experience with using a number line to model addition and subtraction problems.