##
How Many Under the Shell?

**Grade:**

After Okta hides some bubbles under a shell, he
then either adds more bubbles or takes some away. Students have to determine how
many bubbles are left under the shell.

- At the Set Up screen, choose either a number or
Random to determine how many bubbles to start with; then, choose addition,
subtraction, or both. If you choose nothing, the number of bubbles will be
randomly chosen, and you'll receive a mix of addition and subtraction problems.
- Hit
**Start** to go to the problems page.
- Okta will show you some bubbles, hide them under the shell, and then either
add some or take some away. When Okta asks, "How many bubbles are under the
shell?" enter your answer using the keypad.
- If you need to see the demonstration again, click
**Replay**. For a
different problem, click **New**. To select new parameters, click the **Set
Up** arrow.