Suppose That a 1000-L Water Tank Takes 20 Min to Drain

Short Answer

Suppose that a 1000-L water tank takes 20 min to drain and that after t minutes, the amount of water remaining in the tank is V(t) = $\frac { 5 } { 2 }$ (20 - $t ^ { 2 }$ ) liters. What is the average amount of water in the tank during the time it drains?
Enter a reduced fraction of form $\frac { a } { b }$ (no units)