The Brainliest Answer!
Vol.of water= 80*60*6.5
area of the cross section of the pipe= 20*20cm²= .2 *.2 m²
distance the water has to flow so that the tank would be emptied
                             = vol.of the water/area of the cross section
                             =80*60*6.5/(.2*.2) = 78000m=78 km
now,we know that v=d/t
so,t= d/v = 78/15= 5.2 hours

2 5 2
wat 4?u will say and mark other's as the brainliest..
it's ok.. srry for being rude..
its ok