To solve the problem, we will use the principle of set theory to determine the number of families who read none of the newspapers A and B.
### Step-by-Step Solution:
1. **Identify the total number of families**:
- Total families in the city = 15,000.
2. **Identify the number of families reading each category**:
- Families reading A = 8,000.
- Families reading B = 4,000.
- Families reading both A and B = 1,000.
3. **Calculate the number of families reading only A**:
- Families reading only A = Families reading A - Families reading both A and B
- Families reading only A = 8,000 - 1,000 = 7,000.
4. **Calculate the number of families reading only B**:
- Families reading only B = Families reading B - Families reading both A and B
- Families reading only B = 4,000 - 1,000 = 3,000.
5. **Calculate the total number of families reading at least one newspaper**:
- Total families reading at least one newspaper = Families reading only A + Families reading only B + Families reading both A and B
- Total families reading at least one newspaper = 7,000 + 3,000 + 1,000 = 11,000.
6. **Calculate the number of families reading none of the newspapers**:
- Families reading none = Total families - Total families reading at least one newspaper
- Families reading none = 15,000 - 11,000 = 4,000.
### Final Answer:
The number of families who read none of the newspapers is **4,000**.
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