Given, Hose A and B can fill a pool in 5 and 10 min respectively. Concept:/Formula: Total work = Efficiency × Time taken Calculation: Let total work be LCM of (10, 5) = 10 unit Efficiency of A = 2 units Efficiency of B = 1 unit Work done by A and B in 2 min = (2 + 1) × 2 = 6 unit ⇒ Remaining work = 10 – 6 = 4 unit ∴ A completes the remaining work in 4/2 = 2 min