**Title**

You Make The Call (John Long)

**Goals**

Students should use the addition and multiplication principles in order to solve the problems.

**Abstract**

This activity, which is set in the context of finding how many phone numbers can be made, explores the addition and multiplication principles of probability. This activity is envisioned to be implemented after students have been introduced to this principle.

**Problem Statement**

Remind students that just recently 2 new area codes were added to Colorado's phone system. As a matter of fact, communities add new prefixes to their phone numbers all the time. These problem will investigate the number of new phone numbers that are made by adding new prefixes.

**Instructors Suggestions**

(1) Set the stage by discussing the "Problem Statement"

(2) Divide the student into small groups and allow them to work through the activity sheet.

(3) Discuss the solutions in a large group.

**Materials**

**Time**

Introduction (5 min.), activity (20 min.), discussion (10 min.).

**Mathematics Concepts**

*Discrete Mathematics Concepts*

Counting and Probability, Addition and Multiplication principals.

**NCTM Standards Addressed**

Problem Solving, Communication, Reasoning, Connections, Discrete Mathematics, Probability

**Colorado Model Content Standards Addressed**

Problem Solving Techniques (5), Linking Concepts and Procedures (6)

**Curriculum Integration**

This activity should be introduced in a probability section of a course at any level of mathematics. This activity is envisioned to be done after introducing addition or multiplication principals.

**Further Investigation**

Find out the number of prefixes on your town phone numbers. How many different number can be made using those? How were phone number made 50 years ago?

**Variation/Comments
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**References/Resources
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