Answer & Solution
Answer: Option D
Solution:
Let the required number of working hours per day be x.
More pumps, Less working hours per day (Indirect Proportion)
Less days, More working hours per day (Indirect Proportion)
\[\left. \begin{gathered}
{\text{Pumps 4}}:3 \hfill \\
{\text{Days}}\,\,\,\,\,\,\,\,{\text{1}}:2 \hfill \\
\end{gathered} \right\}::8:x\]$$\eqalign{ & \therefore 4 \times 1 \times x = 3 \times 2 \times 8 \cr & \Rightarrow x = \frac{{ {3 \times 2 \times 8} }}{{ 4 }} \cr & \Rightarrow x = 12 \cr} $$