## CHAPTER 3: ADDITION AND SUBTRACTION STRATEGIES

**Lesson 6: Using Mental Math to Add**

**Goal**

Add 2-digit numbers by adding tens and then adding or subtracting ones.

**Instructions for Use**

Addition Attack invites you to solve 1- and 2-digit addition problems to stop aliens from landing.

Click “Go,” read the game instructions, then click “Go” again. Read the addition problem at the top of the screen, then, using your mouse, move the cannon below your answer. Click the mouse to shoot at the correct answer, then answer the next problem. Note that the cannon needs to be directly below the answer to hit it.