Question

39 men can build a bridge in 12 days, working 5 hours a day. In how many days will 30 men, working 6 hours a day, complete the work?

• A. 13
• B. 14
• C. 15
• D. 10

Answer 1

The correct option is A

13

Let the required number of days with 30 men working for 6 hours be x.

$\begin{array}{ccc}\text{Number of men}& 39& 30\\ \text{Number of hours}& 5& 6\\ \text{Number of days}& 12& x\end{array}$

Number of men, number of hours and number of days are inversely proportional and work done is constant in both the cases, hence

$\Rightarrow 39\times 12\times 5=30\times x\times 6$

$x=\frac{39\times 12\times 5}{30\times 6}$

$x=13\text{days}$