A conical water tank with vertex down has a radius of 10 feet at the top and is 24 feet high. If water flows out of the tank at a rate of 20 ft3/min, how fast is the depth of the water DECREASING when the water is 6 feet deep?

Problem number 26 of the rhind papyrus says: find a quantity such that when it is added to of itself the result is a 15. the modern day equation that models this problem is x + x = 15. what is the solution to the equation? x = 10 x = 12 x = 15 x = 30