In this lesson, students learn an addition algorithm in which a single digit is recorded for the sum of each place-value position. Students relate this algorithm to an algorithm they worked with in the previous lesson. Students also learn a method for recording a newly composed ten or hundred as “10” or “100,” respectively, above the addends. Students recognize that the new algorithm and new method of recording newly composed tens or hundreds are based on the idea of adding units by place value.

Think about times when students were able to make connections to and build on the ideas of their peers during discussions today. What norms or routines allowed students to engage with other students’ ideas?