Solution:
Let the population in the district = x
[tex]\begin{gathered} Sample\text{ size}=\frac{20}{100}\times x=0.2x \\ Female\text{ teachers }=40 \\ female\text{ proportion in sample}=female\text{ proportion in population} \\ \frac{40}{0.2x}=\frac{number\text{ of female}}{x} \\ Cross\text{ multiply;} \\ number\text{ of female}=\frac{40x}{0.2x} \\ number\text{ of female}=200 \end{gathered}[/tex]Hence, the most reasonable inference about the number of teachers in the district that are female is about 200.
