Question
3 pumps , working 8 hours a day, can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the tank in 1 day ?
Answer: Option D
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)
\[\left. \begin{gathered}
{\text{Pumps 4}}:3 \hfill \\
\,\,\,\,\,\,{\text{Days 1}}:2 \hfill \\
\end{gathered} \right\}::8:x\]
$$\eqalign{
& \therefore {\text{ }}4 \times 1 \times x = 3 \times 2 \times 8 \cr
& \Leftrightarrow x = \frac{{\left( {3 \times 2 \times 8} \right)}}{{\left( 4 \right)}} \cr
& \Leftrightarrow x = 12 \cr} $$
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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)
\[\left. \begin{gathered}
{\text{Pumps 4}}:3 \hfill \\
\,\,\,\,\,\,{\text{Days 1}}:2 \hfill \\
\end{gathered} \right\}::8:x\]
$$\eqalign{
& \therefore {\text{ }}4 \times 1 \times x = 3 \times 2 \times 8 \cr
& \Leftrightarrow x = \frac{{\left( {3 \times 2 \times 8} \right)}}{{\left( 4 \right)}} \cr
& \Leftrightarrow x = 12 \cr} $$
Was this answer helpful ?
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