Lesson 14

The purpose of this lesson is for students to apply their understanding of adding two-digit numbers to a real-world context.

This lesson is optional because it does not address any new mathematical content standards. This lesson does provide students with an opportunity to apply precursor skills of mathematical modeling. In previous lessons, students found the value of sums within 100 using methods based on place value and the properties of operations, including adding tens and tens and ones and ones, and adding on by place.

In this lesson, students apply these methods to make sense of and solve real-world problems within 100. Students may use base-ten representations or equations to represent their thinking. In the warm-up, they are introduced to a food drive context. In the first activity, they solve problems which involve combining quantities of collected cans in various ways. In the second activity, students make choices about which numbers to combine based on their values and the constraints of the problem. Students may use trial and error to reach the target value. This gives them an opportunity to persevere in problem solving (MP1).

When students make and articulate mathematical choices and adhere to mathematical constraints, they model with mathematics (MP4).

Reflect on a time your thinking changed about something in class recently. How will you alter your teaching practice to incorporate your new understanding?