## CHAPTER 6: ADDITION AND SUBTRACTION

**Lesson 7: Relating Subtraction to Addition**

**Goal**

Use addition and subtraction strategies to calculate differences.

**Instructions for Use**

Cross the Swamp has you solve addition and subtraction problems by providing the missing symbol and number. Use both addition and subtraction strategies to calculate the differences between the numbers.

Select “Addition and Subtraction,” then click “0–100” under “Number Level.” Click on one of the two flashing logs. Read the math problem on the calculator, and figure out how to get to the last number by adding or subtracting. On the calculator, click on “+” or “−,” and then enter the numbers to make the math problem correct. If you need help, click a “Help” frog to look at a 100 chart. Continue this process until the monkey gets across the swamp.

Number Pyramid has you complete addition and subtraction sentences.

Select “Hard” then click “Play” to begin. Read the problem at the top of the screen, then select an answer to fill in the dotted line from the numbers below. Continue answering questions to help Molly get out of the pyramid.