## CHAPTER 3: ADDITION AND SUBTRACTION STRATEGIES

**Lesson 10: Adding 2-Digit Numbers **

**Goal**

Add 2-digit numbers using your own strategies.

**Instructions for Use**

Adding Two-Digit Numbers provides 2-digit addition problems for you to solve and check their answers.

Scroll down to the grey area labelled “Practice.” Click “Start” and answer the addition problem. Click “Check” to check your answer. Click “Start” again to try another problem.

Addition has you solve 2-digit addition problems by choosing pairs of numbers that add to a given sum.

Read the Try This instructions and click the OK button. You need to fix each gap in the slide. Click and drag a piece of tubing to a gap, then click and drag a second piece of tubing. The numbers on the tubing need to add to 20. Pick pairs of numbers for each gap in the slide. Once you are done, the person will slide down to the water! Then, you can proceed to the next problem, where you have to pick pieces of tubing that add to 100.

After you have completed that problem, you can select what sum you want to reach (from 30 to 90) using the red arrow buttons. Select a sum and complete the problem again.