Given: Ram alone can complete a work in 20 days Shyam alone can complete a work in 15 days Formula: Total work = Efficiency × Time Calculation: Total work = 60 units (LCM of 20 and 15) Efficiency of Ram = 3 units/day Efficiency of Shyam = 4 units/day Work done by Ram in 3 days = 3 × 3 = 9 units Remaining work = 60 – 9 = 51 units ∴ Time taken by Ram and Shyam remaining work = 51/(3 + 4) = 51/7 days