we have that
The surface area of the pyramid is equal to the area of its square base plus the area of its four triangular faces
step 1
Find out the area of the square base
A=15^2
A=225 ft2
step 2
Find out the area of one triangular face
the area of a triangle is equal to
A=(1/2)(b)(h)
we have
b=15 ft
h ----> is the slant height
To find out the slant height, apply the Pythagorean Theorem
h^2=10^2+(15/2)^2
h^2=100+56.25
h=12.5 ft
therefore
A=(1/2)(15)(12.5)
A=93.75 ft2
step 3
The surface area is equal to
SA=225+4(93.75)
SA=600 ft2 and the slant height is 12.5 ft
