Question

A contractor undertakes to complete a road 360 m long in 120 days and employs 30 men for work. After 60 days he finds that only 120 m length of the road has been made. How many more men should he employ so that the work may be complete in time?
(A) 20
(B) 30
(C) 15
(D) 45

Answer 1

Hint: Find the number of days and length of the road left to complete the work. By unitary method find the number of men required to complete the remaining work. Subtract it from existing men to get the required value.

Complete step-by-step solution:
As per the contract 360 meters road is to be completed in 120 days
And 120 metres road has already completed in 60 days
Days left$=~120-60=60days$
Length of road left$=360-120=240meters$
In 60 days 120 meters complete by 30 men
We can also say that in 60 days 1 meter can be completed by $\dfrac{30}{120}=\dfrac{1}{4}man$
So, in 60 days 240 meters can be completed by $\dfrac{1}{4}\times 240=60men$
Number of extra men should be employed =Number of men required – number of existing men$=60-30=30$
This is the required solution.
So, (B) is the correct option of the given question.

Note: We are getting that the men required for the work to be completed is 60. It should be subtracted from the number of existing men i.e. 30 as in the question it is asked ‘how many more men should be employed’. Hence the solution is $=60-30=30$.