# Surf for More Math

## Lesson 1 - Modelling Addition and Subtraction

Use this interactive activity to encourage students to have fun on the Web while learning about modelling addition and subtraction. Students can try this activity on their own or in pairs.

### Goal

Model, record and explain addition and subtraction.

### Instructions for Use

I Know That lets students model addition and subtraction.

To use I Know That, click on the "Skip Counting" button. Click the "Maybe Later" button. Then click on the "Give Me a Problem" button on the scratch pad. Problems are presented on the PDA screen.

Use the counters (below the trash can) to make sets and practice skip counting. Click and drag the counters in or out of the counter box, the corresponding number is displayed in the "How many?" box.

Counters are shown in the counter box (the main workspace) along with the total number in the set. To change the number of counters in the box, drag numbers in or out of the counter box; or click on one of the numbers above the counter box.

To use the Counter group, (below the counters), click on a number to select the counter group to use in skip counting. When you click on one of the numbers in the counter group, the counter group changes and the corresponding number sequence is displayed.

Click on one of the numbers (the line above the trash can) to change the set of counters in the counter box, and the number displayed in the "How many?" box.

Click the "New" button to clear the scratch pad and select a different counter.

To remove counters from the counter box, click and drag them into the trash can.