How many numbers are tehre in all which consist of 5 digits?

Answer

To find out how many 5-digit numbers there are in total, we need to consider the constraints on the digits of a 5-digit number.

1. **Understanding the Structure of a 5-Digit Number**:
A 5-digit number can be represented as \(d_1 d_2 d_3 d_4 d_5\), where \(d_1\) is the first digit and \(d_2, d_3, d_4, d_5\) are the subsequent digits.

2. **Constraints on the First Digit**:
The first digit \(d_1\) cannot be 0 (since it would then not be a 5-digit number). Therefore, \(d_1\) can take any value from 1 to 9. This gives us 9 possible choices for \(d_1\).

3. **Choices for the Remaining Digits**:
The remaining digits \(d_2, d_3, d_4, d_5\) can be any digit from 0 to 9. This means each of these digits has 10 possible choices (0 through 9).

4. **Calculating the Total Number of 5-Digit Numbers**:
- For \(d_1\): 9 choices (1 to 9)
- For \(d_2\): 10 choices (0 to 9)
- For \(d_3\): 10 choices (0 to 9)
- For \(d_4\): 10 choices (0 to 9)
- For \(d_5\): 10 choices (0 to 9)

Therefore, the total number of 5-digit numbers can be calculated as:
\[ \text{Total 5-digit numbers} = 9 \times 10 \times 10 \times 10 \times 10 \]

5. **Performing the Calculation**:
\[ = 9 \times 10^4 \]
\[ = 9 \times 10000 \]
\[ = 90000 \]

Thus, the total number of 5-digit numbers is **90,000**.