260/4 = 65 square inches is area of a side
area of a side = baseheight/2 = base 13/2
65 = b13/2
130=b13
b = 10 so the side length equal 10 inches
area of base = 1010 = 100
volume of a pyramid = area of base time height /3
(the height of pyramid)^2 = 13^2 - 5^2
h^2 = 169 -25 = 144
h = 12
V = area of base time height /3 = 10012/3 = 400 cubic inches
hope this will help you
