2.OA.1

Standard

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. (See Table 1)

Student language:

"I can use strategies to solve addition word problems."
"I can use strategies to solve subtraction word problems."

Explanation

About the Math, Learning Targets, and Rigor

This standard calls for calls for students to add and subtract numbers within 100 in the context of one- and two-step word problems. Students should have ample experiences working on all the subtypes of problems illustrated within Table 1 and that have unknowns in all positions, including:

It is important to attend to the difficulty level of the problem situations in relation to the position of the unknown.

Least Complex: Result Unknown, Total Unknown, and Both Addends Unknown problems
Medium Difficulty: Change Unknown, Addend Unknown, and Difference Unknown
Most Complex: Start Unknown and versions of Bigger and Smaller Unknown (compare problems).

This standard also calls for students to solve one- and two-step problems. EXPECT students to use drawings, equations, place value blocks (base 10), number line, etc. to show, solve and explain their reasoning. Just explaining by telling the steps of the procedure will not be enough. Students need to understand the operations and the process. Instead of asking for the “answer”, say: “Using “the model,” “the relationships,” “the structure,” or “justify your answer.”

Common Misconception

Students might rely on a key word or phrase in a problem to suggest an operation that will lead to an incorrect solution. They might think that the word left always means that subtraction must be used to find a solution. Students need to solve problems where key words are contrary to such thinking.

For example, the use of the word left does not indicate subtraction as a solution method:

It is important that students do not rely on using key words to solve problems. The goal is for students to make sense of the problem and understand what it is asking them to do, rather than search for “tricks” and/or guess at the operation needed to solve the problem.

Resources

Videos

Instructional Video (0:59 - 4:24)
Khan Academy
Learn Zillion

EngageNY Lessons

Extra Practice

Released Assessment Questions

2.OA.1-2 Student Example

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