A worker had his monthly salary of ₦3500.00 increased to ₦5000.00. What was the percentage increase? (correct your answer to 1 decimal place).

The increase is the difference between the new salary and the original salary.

$$\text{Increase} = \text{New Salary} - \text{Original Salary}$$ $$\text{Increase} = \text{N}5000.00 - \text{N}3500.00$$ $$\text{Increase} = \text{N}1500.00$$

The percentage increase is the increase divided by the original salary, multiplied by 100%.

$$\text{Percentage Increase} = \frac{\text{Increase}}{\text{Original Salary}} \times 100\%$$ $$\text{Percentage Increase} = \frac{\text{N}1500.00}{\text{N}3500.00} \times 100\%$$ $$\text{Percentage Increase} = \frac{15}{35} \times 100\%$$ $$\text{Percentage Increase} = \frac{3}{7} \times 100\%$$ $$\text{Percentage Increase} \approx 0.42857 \times 100\%$$ $$\text{Percentage Increase} \approx 42.857\%$$

Rounding $42.857\%$ to one decimal place gives $42.9\%$.

$$\text{Percentage Increase} \approx 42.9\%$$

The percentage increase in salary is $\boxed{\text{42.9\%}}$.