[tex]1\ in=2.54\ cm\ \ \Rightarrow\ \ 1\ cm= \frac{1}{2.54}\ in \ \ \Rightarrow\ \ 5\ cm= \frac{5}{2.54}\ in\\ \\10\ in\ \cdot12\ in\ \cdot 5\ cm=120\cdot \frac{5}{2.54}\ in^3\approx283.5\ in^3\\ \\\\1\ gallon=231\ in^3\ <\ 283.5\ in^3\\\\\\Ans.\ 1\ gallon\ of\ paint\ will\ fit\ in\ the\ paint\ tray.[/tex]