A contractor agreed to finish a work completely in 150 days,he employed 75 men each working 8 hours daily. After 90 days, only 2/7 of the work was completed.How many workers he should increase so that the work can be completed on time if each working now work for 10 hours a day,

Work done in 90 days = 75 men × 8 hours × 90 days = 54000 man-hours. This represents 2/7 of total work, so remaining work = 5/7 of total = 135000 man-hours. Time left = 60 days at 10 hours/day = 600 hours. Men needed = 135000/600 = 225 men. Additional workers = 225 - 75 = 150 men. The question asks for the number of workers to increase, and 150 is closest to option D (150).