If we consider that the pyramid has a solid "bottom"...the area of this "bottom" = 7.22 = 51.84 sq units
And subtracting this from 256.7 gives the total area of the sides = 204.86 sq units. And the area of each side is 1/4 of this = 51.215 sq units
And since each side is a triangle with a base of 7.2, we have
51.215 = (1/2)*7.2* h
51.215 = 3.6 * h divide both sides by 3.6
h = about 14.23 units = the slant height
