We use the definition of the volumes of each figure in order to calculate the diameter of the cylinder. We calculate as follows:
V(cylinder) = V(rectangular prism)
πr²h = lwh
from the given, height of the cylinder = height of the prism
πr² = lw
πr² = 5.3(2.7)
r = 2.13
D=2r = 4.27 mm