Question

A square pyramid has a base area of 25 ft2. The pyramid’s total surface area is 105 ft2.

What is the area of each triangular face?

Answer 1

`Area\ of\ pyramide=area\ of\ square+4\cdot\ area\ of\ triangulars\\\\A_p=a^2+4\cdot(ah)/(2)\\\\a^2=25\\a=5\\\\105=25+4\cdot(5h)/(2)\\105-25=2\cdot5h\\80=10h\ \ \ \ |:10\\h=8\\\\A_t=(5\cdot8)/(2)=(40)/(2)=20\ ft^2\\\\Each\ triangular\ has\ 20\ ft^2`