A beaker contains \(100\) milligrams of a solution of salt and water that is \(x\%\) salt by weight such that \(x<90.\) If the water evaporates at a rate of \(y\) milligrams per hour, how many hours will it take for the concentration of salt to reach \((x+10)\%,\) in terms of \(x\) and \(y?\)
(A) \(x^xy^y=\dfrac{24^3}2\)
(B) \(\dfrac{1000+99x}{xy+10y}\)
(C) \(\dfrac{100y+100xy}{x+10}\)
(D) \(\dfrac{1000}{xy+10y}\)
(E) \(\dfrac{\sqrt{x+y}}2\)
Answer: D
Source: Manhattan GMAT