How many 6-digit numbers are there in all ?

Answer

To find out how many 6-digit numbers there are in total, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the smallest 6-digit number**:
The smallest 6-digit number is 100000. This is because a 6-digit number cannot start with 0.

2. **Identify the largest 6-digit number**:
The largest 6-digit number is 999999. This is the highest number that can be formed with 6 digits.

3. **Calculate the total number of 6-digit numbers**:
To find the total number of 6-digit numbers, we subtract the smallest 6-digit number from the largest 6-digit number and then add 1 (to include both endpoints in our count).
\[ \text{Total 6-digit numbers} = (\text{Largest 6-digit number} - \text{Smallest 6-digit number}) + 1 \]
Plugging in the values:
\[ \text{Total 6-digit numbers} = (999999 - 100000) + 1 \]

4. **Perform the subtraction**:
\[ 999999 - 100000 = 899999 \]

5. **Add 1 to the result**:
\[ 899999 + 1 = 900000 \]

6. **Conclusion**:
Therefore, the total number of 6-digit numbers is **900000**.