A rectangular box has six faces. The surface area is given by the sum of the area of those faces. Parallel faces have the same area, therefore, we just need to calculate the area of three of them and multiply by 2. The surface area of our gift box is:
[tex]\begin{gathered} S=2(60\times30+60\times10+30\times10) \\ =2(1800+600+300) \\ =2(2700) \\ =5400 \end{gathered}[/tex]The surface area of the box is 5400 cm².
