Lesson 9

Add 2 Two-digit Numbers

Lesson Purpose

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.

Lesson Narrative

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.

  • Action and Expression
  • MLR7

Learning Goals

Teacher Facing

  • Add 2 two-digit numbers within 100, with composing a ten, in a way that makes sense to them.

Student Facing

  • Let’s add two-digit numbers.

Required Materials

Required Preparation

CCSS Standards


Lesson Timeline

Warm-up 10 min
Activity 1 20 min
Activity 2 15 min
Lesson Synthesis 10 min
Cool-down 5 min

Teacher Reflection Questions

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

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