# Surf for More Math

**CHAPTER 3: ADDITION AND SUBTRACTION ** STRATEGIES

**Lesson 4: Using Mental Math to Add and Subtract**

Use these interactive activities to encourage students to have fun on the Web while learning about using mental math to add and subtract. Students can try these activities on their own or in pairs.

**Goal**

Add and subtract 1-digit and 2-digit numbers using mental math strategies.

**Builds Upon**

Student Book page 64

**Instructions for Use**

Tumbleweed's MathMaze allows students to use mental math strategies to add and subtract as they proceed through a maze.

First choose Medium. Click on the “Pop-o-Matic” die in the blue circle to start playing. Read the addition or subtraction problem in the speech balloon, then click on the answer in the orange arrow below. Click on the die to continue playing and answer the problems until you reach the “Finish” circle.

Cross the Swamp has students use mental math to add and subtract as they help a monkey cross a swamp.

Choose the game “Addition and Subtraction” and number level “0-20.” 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.

Add It Up allows students to practise mental math strategies to add up to a target number.

Click “Play” to start. You have 100 seconds to click on numbers in the grid to add up to the number on the right. If you reach the target number, the numbers you selected will disappear, the counter will reset, and a new target number will appear. If the selected numbers do not add up to the target number, the selected numbers will appear again.

Addition and Subtraction Practice (SMART Notebook-Compatible) allows students to practise using mental math to answer addition and subtraction questions while being timed. You should set this activity up for students. *You will need to adapt the SMART Notebook file so that there are no questions that involve the addition or subtraction of two 2-digit numbers *(these topics are covered in Lessons 6 and 7). You may want to modify the file in other ways to suit your class.

On each page, set the timer and answer as many questions as you can in 30 seconds.