I think what you meant here is that the limestone is in a shape of a square pyramid. Knowing the shape, we must also know the formula for its volume:
V=s²h/3, where
s is the side of the square base
h is the vertical height of the pyramid
First, you find the area of the base s² from the known volume of the larger pyramid.
16,000 = s²(30)/3
s² = 1,600
Then, assuming both pyramids have equal areas of bases, we can use this value for the smaller pyramid. We can determine its volume to be
V = (1,600)(24)/3 = 12,800
Thus, the scale factor for the small pyramid to the big pyramid is 12,800/16,000 or 4/5.