To find the length of one side of the cardboard box (s), we need to solve the equation \( s^3 = 400 \).
To do this, take the cube root of both sides:
\[ s = \sqrt[3]{400} \]
Now, we can calculate \( \sqrt[3]{400} \):
\[ s \approx 7.368 \]
Therefore, the length of one side of the box is approximately 7.37 inches.