A conical reservoir is 50m deep and 200m across the top. Water is being pumped in at a rate of 7000m^3/min, and at the same time, water is being drained out at a rate of 9000 m^3/min. What is the change in diameter when the height of the water in the reservoir is 20m?
The Attempt at a Solution
2.785-3.581 = -0.796 m/min
my answer, however, is supposed to be -1.6m/min