Given: Time taken by A, B and C to fill/empty the tank completely = 8, 16 and 32 hours respectively. Calculation: Part filled by A in 1 hour = 1/8 Part filled by B in 1 hour = 1/16 Part filled by C in 1 hour = – 1/32 (empty) Part filled in 1 hour = 1/8 + 1/16 – 1/32 Part filled in 1 hour = 5/32 Total time = 32/5 hrs ⇒ 6.4 hours ⇒ 6 hours + 0.4 × 60 min ⇒ 6 hours 24 min