40 men could finish a work in 28 days but when some more men joined the work was finished in less than 3/4th of the time. Find the number of more men joined.

Total work = 40 × 28 = 1120 man-days. New completion time < 3/4 × 28 = 21 days. New workers = 40 + x, completing in < 21 days: (40+x) × 21 > 1120, so 40+x > 53.33, meaning x ≥ 14. With 14 more men (54 total), time = 1120/54 ≈ 20.74 days which is less than 21. Option A (12 more) gives 22.22 days, Option B (13 more) gives 21.13 days - both exceed 21 days.