How many numbers are there between 100 and 1000 such that 7. is in the units places?

Answer

To find out how many numbers between 100 and 1000 have 7 in the unit's place, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Range**: We are looking for three-digit numbers between 100 and 1000. This means our numbers will range from 100 to 999.

2. **Fix the Unit's Place**: Since we need 7 to be in the unit's place, we can represent our three-digit number as \( \_ \_ 7 \), where the first two digits can vary.

3. **Determine the Hundreds Place**: The hundreds place can be filled with any digit from 1 to 9 (since we cannot have 0 in the hundreds place for a three-digit number). Therefore, we have 9 options for the hundreds place (1, 2, 3, 4, 5, 6, 7, 8, 9).

4. **Determine the Tens Place**: The tens place can be filled with any digit from 0 to 9. Therefore, we have 10 options for the tens place (0, 1, 2, 3, 4, 5, 6, 7, 8, 9).

5. **Calculate the Total Combinations**:
- The total number of combinations for the hundreds and tens places is calculated by multiplying the number of choices for each place:
\[ \text{Total Combinations} = (\text{Choices for Hundreds}) \times (\text{Choices for Tens}) = 9 \times 10 = 90 \]

6. **Conclusion**: Therefore, there are 90 three-digit numbers between 100 and 1000 that have 7 in the unit's place.

### Final Answer:
The total number of numbers between 100 and 1000 such that 7 is in the unit's place is **90**.