Answer:26.28 cm
Explanation:
In permeability test k is given by
[tex]k=\dfrac{qL}{Ah}[/tex]
where
k=Coefficient of permeability
q=Length of specimen
A=area of cross-section
h=constant head causing flow
[tex]h=\dfrac{q\times L}{A\times k}[/tex]
[tex]h=\dfrac{130\times 20}{60\times 78.5\times 2.1\times 10^{-2}}[/tex]
[tex]h=26.28\ cm[/tex]