Indian Institute of Foreign Trade 2011 Solved Paper

It is given that a man is able to perform the work equal to the same done by 2 boys. Hence, we can assume that In Bilaspur village 21=(12+18/2) men completed construction of a primary health center in 60 days, by working for 7.5 hours a day.
Hence, total men hours required to completed the primary health center in Bilaspur =7.5×21×60=9450.
Let us assume that 'n' be the number of boys required to help 21 men to complete the work in Harigarh in 50 days by working 9 hours a day.
Therefore, we can say that
⇒2×9450=50×9×(21+

t

2

)
⇒42=21+

t

2

⇒t=42
Hence, option D is the correct answer.