Plainville Public Schools

In this unit, students learn to solve new types of addition and subtraction story problems and relate the quantities in the stories to equations.

In kindergarten, students solved a limited number of types of story problems within 10 (Add To/Take From, Result Unknown, and Put Together/Take Apart, Total Unknown, and Both Addends Unknown). They represented their thinking using objects, fingers, mental images, and drawings. Students saw equations and may have used them to represent their thinking, but were not required to do so.

Here, students encounter most of the problem types introduced in grade 1: Add to/Take From, Change Unknown, Put Together/Take Apart, Unknowns in All Positions, and Compare, Difference Unknown. The numbers are kept within 10 so students can focus on interpreting each problem and the relationship between counting and addition and subtraction. This also allows students to continue developing fluency with addition and subtraction within 10.

As they solve problems, students analyze and write equations and consider the meaning of the equal sign. They may initially see it as a prompt for the answer to a question, which makes it difficult to interpret equations such as 7=5+2. Developing an understanding of the equal sign is particularly important in solving missing-addend problems. For example:

Students may see a subtraction problem, represented by 9−4=5, or a missing-addend problem, represented by 4+5=9. This work also highlights that multiple equations can often be written for each story problem.

It is more important for students to explain the relationship between the equation they wrote and the story, than for their equations to match the story or their solution method.

To help students think about the meaning of each number in an equation, a box is placed around the answer to the question in the problem. In the last section, students work with equations where an empty box represents the unknown.

In the next unit, students will solve addition and subtraction problems within 20 and work with equations with a symbol for the unknown in all positions, and further develop their fluency within 10. 

Throughout the unit

Number Talks are used to encourage students to develop counting on and counting back methods as they continue to develop fluency with addition and subtraction within 10. Students are introduced to new centers that support the work of this unit. Centers to revisit from previous units are also suggested in each section. Feel free to incorporate other centers that have been previously introduced based on student need and interest.