Answer: 256 cm squared.
Explanation:
The surface area of an open cuboid formula is as follows: Surface Area = 2(lw) + 2(lh) + 2(hw). This is what we will use to get an answer.
Substitute length, width and height variables for your measurements into the formula to get the following equation and solve it:
SA = 2(20 x 4) + 2(20 x 2) + 2(2 x 4)
SA = 2(80) + 2(40) + 2(8)
SA = 160 + 80 + 16
SA = 256 cm squared
Therefore, the surface area of this open cuboid is 256 centimetres.
I hope this helped and have a good day! :)