# Surf for More Math

**CHAPTER 3: ADDITION AND SUBTRACTION ** STRATEGIES

**Lesson 4: Building on Doubles **

Use these interactive activities to encourage students to have fun on the Web while learning about strategies for addition and subtraction. Students can try these activities on their own or in pairs.

**Goal**

Use doubles, doubles + 1, and doubles + 2 to determine basic addition facts to 18.

[C, ME, R, V]

**Instructions for Use**

**Adding Doubles to 20** lets students practice adding doubles.

To use Adding Doubles to 20, input the answers in the text boxes. Click the "Check Answers" button to see if the answers are correct.

**Adding Doubles Plus One** lets students practice adding doubles plus one.

To use Adding Doubles Plus One, input the answers in the text boxes. Click the "Check Answers" button to see if the answers are correct.