The purpose of this lesson is for students to put numbers 1–20 in order and use their knowledge of the count sequence to identify 1 more or 1 less than a given number.

This lesson is optional, because the standards do not require students to compare groups of objects or written numbers beyond 10. This lesson does give students additional work with the 1–20 number sequence.

In a previous lesson, students initially counted out objects and added or subtracted 1 object to determine 1 more or 1 less than a given number. In this lesson, students continue working on identifying 1 more and 1 less than a given number up to 20, without objects, and relating 1 more and 1 less to the count sequence (MP8).

If students need additional support with the concepts in this lesson, refer back to Unit 6, Section B in the curriculum materials.

Were you able to circulate and hear student thinking while students worked together in the second activity? If so, what routines or structures helped students work independently? If not, what routines or structures can you establish to ensure that you are able to circulate and talk to students as they work in groups?