Pipe A can fill a tank in 16 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 option:
A) 20
B) 24
C) 23
D) 22
E) None of these
Explanation:   Let the pipe B be closed after x minutes.   30/16 - x/24 = 1 =&gt; x/24 = 30/16 - 1 = 14/16   =&gt; x = 14/16 * 24= 
<gadget id="calculator">14/16 * 24</gadget>
<output>21</output>
21.   ANSWNone of theseR IS None of these
<result>E</result>
Pipe A can fill a tank in 16 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?