A biologist studied the population of rats in a barn. He found that the average natality was 250, average mortality 240, immigration 20 and emigration 30. The net increase in populations is :

Options

A. `05`
B. zero
C. `10`
D. `15`

Answer

To find the net increase in the population of rats in the barn, we can use the following formula:

**Net Increase in Population = (Natality + Immigration) - (Mortality + Emigration)**

### Step-by-Step Solution:

1. **Identify the Values**:
- Natality (birth rate) = 250
- Mortality (death rate) = 240
- Immigration (individuals moving into the population) = 20
- Emigration (individuals moving out of the population) = 30

2. **Calculate the Total Births and Immigration**:
- Total births and immigration = Natality + Immigration
- Total = 250 + 20 = 270

3. **Calculate the Total Deaths and Emigration**:
- Total deaths and emigration = Mortality + Emigration
- Total = 240 + 30 = 270

4. **Calculate the Net Increase in Population**:
- Net Increase = (Natality + Immigration) - (Mortality + Emigration)
- Net Increase = 270 - 270 = 0

5. **Conclusion**:
- The net increase in the population of rats in the barn is **0**.

### Final Answer:
The net increase in the population is **0**.

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