[
  "Find tank volume in litres: 1.2 m = 120 cm. 120^3 / 1000 = 1,728 L.",
  "Water to lose: 90% - 50% = 40% of 1,728 = 691.2 L.",
  "Time = 691.2 / 0.5 = 1382.4 sec, rounds to 1382 seconds."
]