12 men working 8 hours per day complete a piece of work in 10 days. To complete the same work in 8 days, working 15 hours a day, the number of men required, is:
(a)4
(b)5
(c)6
(d)8
Answer
Answer (as printed): D
Explanation
Let the required number of men be $x$. Less days, More men (Indirect Proportion) More working hrs per day, Less men (Indirect Proportion) Days $$\left.\begin{array}{c} 8: 10 \\ 15: 8 \end{array}\right\}:: 12: x$$ $\therefore 8 \times 15 \times x=10 \times 8 \times 12$ $\Leftrightarrow x=\frac{10 \times 8 \times 12}{8 \times 15} \Leftrightarrow x=8$.
Explanation as extracted from the printed page; notation may be imperfect.