Pipe P can fill a tank in 16 minutes and pipe Q cam empty it in 24 minutes. If both the pipes are opened together after how many minutes should pipe Q be closed, so that the tank is filled in 30 minutes? Answers:
A) 21	B) 20	C) 25	D) 22	E) 40
30/16-X/24==&gt;1   X/24=30/16-1==14/16   X=14/16*24= 
<gadget id="calculator">14/16*24</gadget>
<output>21</output>
21   21NSWER 21
<result>A</result>
Pipe P can fill a tank in 16 minutes and pipe Q cam empty it in 24 minutes. If both the pipes are opened together after how many minutes should pipe Q be closed, so that the tank is filled in 30 minutes?