Lesson 9

The purpose of this lesson is for students to add 2 two-digit numbers within 100 in any way that makes sense to them, including composing a ten.

In previous lessons, students added a one-digit number and a two-digit number with composing a ten. They also added 2 two-digit numbers without composing a new ten. They discussed methods based on place value and the properties of operations. They wrote equations to show their thinking.

In this lesson, students add 2 two-digit numbers in any way that makes sense to them. Students may apply methods learned in previous lessons, including methods based on making a new ten or adding tens and tens and ones and ones. Students are not required to write equations, although some may do so.

How effective were your questions in supporting students’ thinking today? What did students say or do that showed they were effective?