Question no. 8 correct solution..
by Deepak
the correct solution is like this... the emptying pipe empty the tank in 8 min it means, it empty 1/8 per min and the filling pipe fill at the rate of 1/15 , so the actual rate of emptying the tank is .. (1/8)-(1/15) =7/90 = 1/12.9 , it means it 12.9 min to empty the full tank , so it would take 12.9/2 = 6.45 min to empty the half tank .. duh..
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