Primary Standards:
MAFS.2.OA.1.1 Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem.
MAFS.2.NBT.2.5 Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
MAFS.2.OA.1.aDetermine the unknown whole number in an equation relating four or more whole numbers. For example, determine the unknown number that makes the equation true in the equations 37 + 10 + 10 = ______ + 18, ? – 6 = 13 – 4, and 15 – 9 = 6 + ⃞.
Content Knowledge:
In this Unit, students will continue to apply their addition and subtraction strategies to solve word problems. In kindergarten and 1st grade, students experienced work with 11 of the 15 common addition and subtraction problem structures, in 2nd grade they will now experience all 15, including the addition of Add To- and Take From- Start Unknown, Compare – Smaller Unknown (w/ “more”), and Compare – Bigger Unknown (w/ “fewer”).
Additionally, 2nd graders will continue their work in representing story problems with equations, including unknowns in all positions. Teaching key words does not help students to develop an understanding of problem situations. Rather, by using concrete models and drawing pictures, students can relate their actions to whether the situation calls for addition or subtraction. In missing addend cases, students will determine what operation makes the most sense for them, as either will result in a correct solution. 2nd graders will continue to apply their understanding and problem-solving skills in future content. They will solve addition and subtraction problems related to length and money. Their comprehension and computations skills with a wider range of problems will help them discover that problem solving connects to all math content.
GCG 1 – Learning Goal: As a mathematician, I can Determine the unknown in an equation relating four or more whole numbers
- Step 1: Find the unknown number in an addition equation using the commutative property
- Step 2: Find the unknown number in an equation using the same operation on both sides relating four or more whole numbers
- Step 3: Find the unknown number in an equation relating four or more whole numbers (same or mixed operations)
GCG 2 – Learning Goal: As a mathematician, I can Solve one-step word problems using place value strategies
- Step 1: Differentiate if a story problem can be represented using addition or subtraction
- Step 2: Directly model and solve the actions in one-step addition and subtraction story problems within 100 (with unknowns in all positions and involving all problem types)
- Step 3: Represent one-step story problems with an equation, including using a symbol to represent the unknown
GCG 3 – Learning Goal: As a mathematician, I can Solve two-step word problems using place value strategies
- Step 1: Directly model and solve the actions in two-step addition and subtraction story problems within 100 (with unknowns in all positions and involving all problem types)
- Step 2: Represent two-step story problems with an equation, including using a symbol to represent the unknown
- Step 3: Write or create a story context to represent one or two-step addition or subtraction situations using a given expression