Answer
given,
thickness of the aquifer = 30 m
distance between the piezometer = 280 m
head difference between them  = 1.4 m
n = 0.3
K= 50 m/day
using Darcy's law
[tex]v = k \dfrac{dh}{dl}[/tex]
[tex]v = 50\times  \dfrac{1.4}{280}[/tex]
v = 0.25 m/day
average linear velocity
[tex]v = \dfrac{v}{n}[/tex]
[tex]v = \dfrac{0.25}{0.3}[/tex]
 v = 0.833 m/day
time to travel
= Â [tex]\dfrac{280}{0.833}[/tex]
= 336 days