To help develop operation sense in students, teachers should provide problems in context that encourage students to show how the operational symbols + and − can be used to express quantities. Rather than a focus on the single numeric answer, the object of this lesson is to have students say and write numeric expressions that represent the numeric quantities described in the problem. An expression is simply another name for a numeric quantity. Equations and inequalities are number sentences. Students often confuse expressions with equations and use the symbol = along with the expression. They should be prompted at this point to simply "express" the quantity described in the problem situation with numbers and operational symbols only. Later they will be asked to show the relationship between numeric quantities with the symbols <, > or = in a number sentence.

Begin with several whole class examples that demonstrate the basic addition/subtraction problem structure. In grade 1, students have written numeric expressions with the symbols + and − with numbers through 20. In this lesson, students will use dry erase boards or slates to write their numeric expression. They must use the numbers in the problem and one of the symbols, + or −, to represent the numeric quantity described in the problem.

Examples:

Laura had 9 pennies. She found 3 on the bus. How many does she have now?

Students should display 9+3 on their boards. Using "every student response", teachers can quickly check for errors. Students might simply write 12. Remind those students that they must use the numbers and either + or − to show how they arrived at 12. Students might also write 3+9. Discuss with the class how this quantity is the same or different than 9+3. Does it show the same relationship?

Sam had 12 pennies. He lost four. How many does he have now?

Now provide problems within the classroom context.

"I measured the distance from the floor to the ceiling. It was 12 feet tall. I measured the distance from the floor to the top of the doorway. It was eight feet tall. How many feet is it from the top of the door to the ceiling?"

"We need 25 cupcakes for our class party. Terry's mom will bring 12. How many more do we need?"

"Juan's mom will bring 12 cupcakes for the class party. Shanika's mom will also bring 12 cupcakes. How many will we have altogether?"

Problems such as these can be built around a single problem situation, such as classroom measurements or class party cupcakes. They should, however, be real and pertinent to the students in your class.

As an assessment, provide students with problem situations and multiple choice responses that show possible number relationships.

As an example:
"In our class, there are 5 fewer students that walk than take the bus. There are 25 students that take the bus. Which expression can be used to find how many more students take the bus than walk?"