Side of cube = 1.2 m = 120 cm<br>
Volume of tank = 120&sup3; = 1,728,000 cm&sup3; = 1,728 L<br><br>
90% full = 0.90 × 1,728 = 1,555.2 L<br>
50% full = 0.50 × 1,728 = 864 L<br>
Volume to leak = 1,555.2 − 864 = 691.2 L<br><br>
Leak rate = 0.5 L/s<br>
Time = 691.2 ÷ 0.5 = 1,382.4 seconds → 1,382 s (nearest second)<br><br>
Final Answer: 1,382 seconds