## CHAPTER 3: DECIMAL NUMBERS

**Lesson 2: Adding and Subtracting Decimals **

Use these interactive activities to encourage students to have fun on the Web while learning about decimal numbers. Students can try these activities on their own or in pairs.

**Goal**

Develop strategies to add and subtract decimals.

**Builds Upon**

Student Book pages 101–105

**Instructions for Use**

**Adding Decimals** allows students to add decimals using decimal models.

To use Adding Decimals, read the instructions and click on “New Problem”. Type in a decimal in the top right box and press “Enter”. Chimes sound and the decimal appears in colour on a 100 grid to the left. Type the second decimal to be added and press “Enter”. Chimes again sound as this decimal appears in colour on a 100 grid below the first. Now type in the sum and press “Enter”. If correct, a lower set of chimes sound. If the sum is wrong, nothing happens until it is corrected. To see the sum on one grid, click on “Rearrange”, or click on “New Problem” to start a new round.

**Addition with One Decimal Digit ** , **Addition with Two Decimal Digits** and **Addition with Three Decimal Digits** allow students to practice their decimal adding skills to one, two, and three places, respectively.

To use these activities, read the instructions and then click on each answer box and type in the answer. If correct, a red check mark will appear next to that answer. If not, a red “**X**” will appear instead. You can correct wrong answers by clicking on them and typing in the correct answer. Click on “Start Again” or “Next Game” to see a new set of problems to solve. No score is kept.

**Subtraction with One Decimal Digit ** and **Subtraction with Two Decimal Digits** allow students to practice their decimal subtracting skills to one and three places, respectively.

To use these activities, follow the same directions as for Addition with One Decimal Digit above.