Pipe A can fill a tank in 8 minutes and pipe B cam empty it in 24 minutes. If both the pipes are opened together after how many minutes should pipe B be closed, so that the tank is filled in 30 minutes? Choose the correct choice from the following choices.
A) 18 B) 27 C) 98 D) 27 E) 66

Rationale: let the pipe b be closed after x minutes . 30 / 8 - x / 24 = 1 = > x / 24 = 30 / 8 - 1 = 11 / 4 = > x = 11 / 4 * 24 = 66 . answer : e
Answer: E