Primary Standards:
MAFS.1.OA.1.1 Use addition and subtraction within 20 10 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
MAFS.1.OA.2.4 Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8.
Connecting Standards:
MAFS.1.OA.4.8 Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ?= 11, 5 = ? – 3, 6 + 6 = ?.
MAFS.1.OA.3.5 Relate counting to addition and subtraction (e.g., by counting on 2 to add 2)
MAFS.1.OA.3.6 Add and subtract within 20, demonstrating fluency for addition and subtraction within 10.
Content Knowledge:
Students are not required to independently read the word problems.
In first grade, a new subtraction structure, comparison, is introduced. To compare quantities or find out how many more/how many less, subtraction is used. This structure is not about an action, but about the relationship between two quantities. This model can be confusing for students when their idea of subtraction is limited to taking away or taking apart a single quantity. There is no change or action in comparison problems. Visuals and models should be utilized for conceptual understanding, and the term difference can be introduced.
Exploring comparison problems with unknowns in different positions again strengthens the connection between the concepts of addition and subtraction. In finding the difference between two values, students may represent a problem with a missing addend rather than use subtraction. Knowing this, they can use a “counting up” strategy to solve rather than subtracting.
GCG 1 – Learning Goal: As a Mathematician, I will be able to Solve Compare Difference Unknown Problems (within 10)
- Step 1: Represent Compare Smaller/Bigger Unknown problems within 10 using concrete tools
- Step 2: Represent Compare Smaller/Bigger Unknown problems within 10 using drawings
- Step 3: Represent Compare Smaller/Bigger Unknown problems within 10 using equations
Learning Goal: As a Mathematician, I will be able to Solve Compare Smaller/Bigger Unknown Problems (within 10)