An engineer undertakes a project to build a road 15 km long in 300 days and employs 30 men for the purpose. After 100 days, he finds only 2.5 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) a . 43  B) b . 45  C) c . 55  D) d . 68  E) e . 60

Rationale: "30 workers working already let x be the total men required to finish the task in next 200 days 2.5 km done hence remaining is 12.5 km also , work has to be completed in next 200 days ( 300 - 100 = 200 ) we know that , proportion of men to distance is direct proportion and , proportion of men to days is inverse proportion hence , x = ( 30 * 12.5 * 100 ) / ( 2.5 * 200 ) thus , x = 75 thus , more men needed to finish the task = 75 - 30 = 45 hence answer is b"
Answer: B