The section modulus (Z) of a hollow circular section with external diameter as D and internal diameter as d, is given by
1
\(Z = \frac{\pi}{30D} [D^5-d^4]\)
2
\(Z = \frac{\pi}{32D} [D^4-d^4]\)
3
\(Z = \frac{\pi}{16D} [D^4-d^4]\)
4
\(Z = \frac{\pi}{32D} [D^2-d^2]\)