A company wants to have 4-digit phone extensions with the first digit not being zero. How many different phone extensions are possible?

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
ISBN:9780079039897
Author:Carter
Publisher:Carter
Chapter5: Linear Inequalities
Section5.1: Solving Inequalities By Addition And Subtraction
Problem 57PFA
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### Determining the Number of Possible 4-Digit Phone Extensions for a Company

A company wants to have 4-digit phone extensions with the first digit not being zero.

---

**Question:**

How many different phone extensions are possible?

---

**Solution:**

To determine the number of different possible phone extensions, consider the following constraints:

1. The phone extension is 4 digits long.
2. The first digit cannot be zero.

**Calculation Strategy:**

1. **First digit options:**
   - Can be any digit from 1 to 9. (9 possible options)
2. **Second, third, and fourth digit options:**
   - Can be any digit from 0 to 9. (10 possible options each)

The total number of different phone extensions can be calculated by multiplying the number of options for each digit:

\[ 9 \times 10 \times 10 \times 10 \]

**Result:**

The number of different 4-digit phone extensions the company can have is:

\[ 9 \times 10^3 = 9 \times 1000 = 9000 \]

Therefore, the company can have **9,000 different phone extensions**.

---

This calculation ensures that the first digit is never zero, meeting the company's constraint for their phone extension system.

### Visualization:

To visualize the options, consider a representation where each position in the 4-digit extension is defined:

- **First digit:** 9 options (1-9)
- **Second, third, and fourth digits:** 10 options each (0-9)

\[
\text{First digit (9 options)} \quad \text{Second digit (10 options)} \quad \text{Third digit (10 options)} \quad \text{Fourth digit (10 options)}
\]

This effectively creates \( 9 \times 10 \times 10 \times 10 = 9,000 \) unique 4-digit extensions. 

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Transcribed Image Text:--- ### Determining the Number of Possible 4-Digit Phone Extensions for a Company A company wants to have 4-digit phone extensions with the first digit not being zero. --- **Question:** How many different phone extensions are possible? --- **Solution:** To determine the number of different possible phone extensions, consider the following constraints: 1. The phone extension is 4 digits long. 2. The first digit cannot be zero. **Calculation Strategy:** 1. **First digit options:** - Can be any digit from 1 to 9. (9 possible options) 2. **Second, third, and fourth digit options:** - Can be any digit from 0 to 9. (10 possible options each) The total number of different phone extensions can be calculated by multiplying the number of options for each digit: \[ 9 \times 10 \times 10 \times 10 \] **Result:** The number of different 4-digit phone extensions the company can have is: \[ 9 \times 10^3 = 9 \times 1000 = 9000 \] Therefore, the company can have **9,000 different phone extensions**. --- This calculation ensures that the first digit is never zero, meeting the company's constraint for their phone extension system. ### Visualization: To visualize the options, consider a representation where each position in the 4-digit extension is defined: - **First digit:** 9 options (1-9) - **Second, third, and fourth digits:** 10 options each (0-9) \[ \text{First digit (9 options)} \quad \text{Second digit (10 options)} \quad \text{Third digit (10 options)} \quad \text{Fourth digit (10 options)} \] This effectively creates \( 9 \times 10 \times 10 \times 10 = 9,000 \) unique 4-digit extensions. ---
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