Answer with explanation:
Time taken by 2, men to build an airstrip = 5 hours
Time taken by 1, men to build the airstrip = 2 × 5
=10 hours
Since ,time is inversely proportional to Number of people working and if rate of doing work is Higher time will be less.
Using Unitary method
[tex]M_{1}T_{1}R_{1}=M_{2}T_{2}R_{2}\\\\R_{1}=R_{2}\\\\T_{2}=4\\\\2 \times 5 \times R_{1}=M_{2}\times 4\times R_{2}\\\\M_{2}=\frac{10}{4}\\\\M_{2}=2.5[/tex]
Number of Men can't be a fraction.So total number of men should be 3 to accomplish the work in 4 Hours.
Earlier 2, men were working to complete the work in 5 days.
Now, 3 men are working to accomplish the work in 4 days.
So,Total number of extra men Added
= 3-2=1
None of the option , matches with the Answer i got.
