## IM Commentary

This task includes three different problem types using the "Add To" context with a discrete quantity; see "1.OA The Pet Snake" for an "Add To" problem with a continuous quantity. Table 1 in the glossary of the CCSSM offers a succinct overview of all addition and subtraction problem types.

Although students should experience and practice with all three problem types, they would not necessarily be introduced at the same time. Please see the K, Counting and Cardinality; K–5, Operations and Algebraic Thinking Progressions Document for in-depth information about issues related to students’ learning of these kinds of problems.

While students are expected to add and subtract fluently within 10 in first grade (1.OA.6), they are not expected to add and subtract fluently within 20 until second grade (2.OA.2).

## Solution

Students may use objects, pictures, or equations to represent their solutions. The solutions show equations with a question mark representing the unknown value, but other symbols are often used. For example, 4 + ? = 11 might also be written

4 + ____ = 11 or 4 + ☐ = 11.

- Total Unknown: There were $11$ children in all.

Possible equation: $7 + 4 =$ ?
- Addend Unknown: $4$ more children came.

Possible equation: $7 +$ ? $= 11$
- Start Unknown: There were $7$ children in the park to start with.

Possible equation: ? $+ 4 = 11$