An engineer undertakes a project to build a road 10 km long in 60 days and employs 30 men for the purpose. After 20 days, he finds only 2 km of the road has been completed. Find the (approximate) number of extra men he must employ to finish the work in time.  Choices:
A) 20
B) 15
C) 30
D) 45
E) 60

Rationale: "30 workers working already let x be the total men required to finish the task in next 40 days 2 km done hence remaining is 8 km also , work has to be completed in next 40 days ( 60 - 20 = 40 ) we know that , proportion of men to distance is direct proportion and , proportion of men to days is inverse proportion hence , x = ( 30 * 8 * 20 ) / ( 2 * 40 ) thus , x = 60 thus , more men needed to finish the task = 60 - 30 = 30 answer : c"
Answer: C