Surface area of a rectangular prism with length 10 meters, width 20 meters, and height 4 meters

640 m^2.

Step-by-step explanation:

There are 6 faces to this prism:

2 with dimensions 20*10 = 2*200 = 400 m^2

and 2*20*4 = 160 m^2

and 2*10*4 = 80 m^2

Total surface area = 400+169+80 = 640 m^2.