In order to find the surface area, we need to calculate the area of each face
As we can see we have 4 triangles that are congruent and a square
First we will calculate the area of one triangle, the formula of the area of a triangle is
where
b is the base
h is the height
in our case
b=11cm
h=8cm
we substitute the values
![A_T=(11\cdot8)/(2)=44\operatorname{cm}^2]()
Then we calculate the area of the square the formula for the area is
s is side
s=11 cm
we substitute in the formula
![A_S=11*11=121\operatorname{cm}^2]()
In order to find the surface area
![SA=4(44)+121=297\operatorname{cm}^2]()