we know that
surface area=2*[area of the base]+perimeter of the base*height
find the area of the base
is an equilateral triangle
b=15/3----> 5 in
applying the law of sines to find the area
Area=(1/2)*b²*sin 60°------> area=(1/2)*5²*sin 60°----> 10.8253 in²
alternative method to find the area of the equilateral triangle
find the h value
applying the Pythagoras theorem
h²=5²-2.5²-----> h=√18.75-----> h=4.33 in
area=b*h/2----> area=5*4.33/2----> 10.8253 in²
surface area=2*[10.8253]+15*4-----> 81.65 in²
the answer is
81.65 in²
