The surface area for a square pyramid is given by
Area = a^2 + 2a sqrt (( a^2)/4 +h^2) (No, I didn't know that...I looked it up)
We have a = 20 we just need to find h
tan (55) = h/10 h= 14.2814
Area = 20^2 + 2(20) sqrt ( 400/4 + 7.14^2) =1097.38 cm^2