Lesson 9 Add 2 Two-digit Numbers

- Let’s add two-digit numbers.

Warm-up Number Talk: Make a Ten

Find the value of each expression mentally.

$38 + 2$
$40 + 3$
$38 + 5$
$38 + 15$

Activity 1 How Did You Find the Value?

Find the value of $17 + 36$ .
Show your thinking using drawings, numbers, or words.

Activity 2 Grab and Add

Students with connecting cube towers.

Problem 1

Round 1:
Grab a handful of towers of ten and a handful of single cubes.

I have cubes and my partner has cubes.
How many cubes do you and your partner have altogether?
Show your thinking using drawings, numbers, or words.

Problem 2

Round 2:

I have cubes and my partner has cubes.
How many cubes do you and your partner have altogether?
Show your thinking using drawings, numbers, or words.

Problem 3

Round 3:

I have cubes and my partner has cubes.
How many cubes do you and your partner have altogether?
Show your thinking using drawings, numbers, or words.

Problem 4

Round 4:

I have cubes and my partner has cubes.
How many cubes do you and your partner have altogether?
Show your thinking using drawings, numbers, or words.

Practice Problem

Problem 1

Find the value of $35 + 48$ .
Show your thinking using drawings, numbers, or words.