A tank is filled in TWELVE hours by three pipes A, B and C. Pipe A is twice as fast as pipe B, and B is twice as fast as C. How much time will pipe B alone take to fill the tank?  Choose the correct choice from the following options:  A) 42 hours  B) 28 hours  C) 55 hours  D) 66 hours  E) 47 hours
1/A + 1/B + 1/C = 1/12 (Given)   Also given that A = 2B and B = 2C   =&gt; 1/2B + 1/B + 2/B = 1/12   =&gt; (1 + 2 + 4)/2B = 1/12   =&gt; 2B/7 = 12   =&gt; B = 42 hours.   42 hoursnswer: 42 hours
<result>A</result>
A tank is filled in TWELVE hours by three pipes A, B and C. Pipe A is twice as fast as pipe B, and B is twice as fast as C. How much time will pipe B alone take to fill the tank?