we know that
[volume of a pyramid]=[area of the base]*height/3
area of the base=3*volume of a pyramid/height---> 3*320 cm³/15 cm---> (64) cm²
area of the base=b²
where
b-----> is the side length of the square base
b=√area of the base-----> b=√(64)-----> b=8 cm
the answer is
the length side of the base is 8 cm
