The cube's water is equally split among 5 cuboids. Total volume is conserved.<br><br>Volume of one cuboid = 20 × 8 × 10 = 1600 cm&sup3;.<br>Total volume of 5 cuboids = 5 × 1600 = 8000 cm&sup3;.<br>So the cube's volume = 8000 cm&sup3;.<br><br>s&sup3; = 8000<br>s = \( \sqrt[3]{8000} \) = 20 cm.<br><br>Final Answer: 20 cm