# 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)

Find the value of

.

Show your thinking using drawings, numbers, or words.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.

Add the numbers.

Write equations to show your thinking.

## Problem 5 (Exploration)

Elena has a way to find the value of

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

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

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

Which method is your favorite?

Solveusing your favorite method.

## Problem 7 (Exploration)

Clare wrote some expressions.

Each expression makes a ten.

She spilled water on her work.

Find the digit that could be under each water mark.