# Section C: Practice Problems Make a Ten: Add Within 100

## Section Summary

Details

We learned to add any 2 two-digit numbers within 100 and write equations to represent our methods.

We added tens and tens and ones and ones.

We added ones first to make a new ten.

## Problem 1 (Lesson 9)

Find the value of .
Show your thinking using drawings, numbers, or words.

## Problem 2 (Lesson 10)

1. Find the value of .
Show your thinking using drawings, numbers, or words.

2. Can you find the value in a different way?

## Problem 3 (Lesson 11)

Use your favorite method to find the value of .
Why do you like the method you chose?

## Problem 4 (Lesson 12)

Choose a two-digit number to add to 46 so that you make a new 10.
Write equations to show your thinking.

## Problem 5 (Exploration)

Elena has a way to find the value of without making a 10. Here is her work.

1. Explain why Elena’s work is correct. Use connecting cubes if it is helpful.

2. Use Elena’s method to find the value of .

## Problem 6 (Exploration)

Diego and his friends are working on the same addition problem.

Diego’s method

Lin’s method

Priya’s method

1. What is the addition problem Diego and his friends are working on?

2. Which method is your favorite?