A hot water tank is to be filled with water by the technicia
     A hot water tank is to be filled with water by the technician that has a volume of V with units of m^3. He plans to use a hose nearby which has a diameter of D, in m. The average velocity of the water leaving the hose is v, having units of m/s. Obtain a relation to determine the amount of time (t) in seconds (s) it will take to fill the tank. 
  
  Solution
Given that,
Volume of the tank is V in m3.
Diameter of the hose is D in m
Average Velocity is v in m/sec
time is t in sec.
We know
Cross section of circular hose A= (/4)*D2
volume flow rate/Discharge per second Q= Av
=(/4)*D2*v
Time taken to fill the tank= V/Q
But we have Q=(/4)*D2*v
therefore
Amount of Time required=(V)/(/4)*D2*v
t =4V/(D2*v) sec

