A cistern of 475 litres is completely filled using pipes A and B, with Pipe A being open for 5 more hours than pipe B. If we are to interchange the operating hours of the two pipes than pipe A would have pumped half the water as much as pipe B, then find the time for which pipe B was open. Also, given that if the two pipes were open simultaneously the tank would fill in 19 hours. Choose the correct choice from the following options:
A) 10 h	B) 14 h	C) 16 h	D) 20 h	E) 24 h
DETAILED SOLUTION   The 475 litres is filled in 19 hours by the two pipes when they are opened simultaneously.   Therefore, rate of water flow by A and B,   A + B = 47519 = 25 litres/hour………….(1)   Let pipe B was opened for t hours   Then, pipe A was opened for t + 5 hours   A x (t+5) + B x t = 475   (A + B) x t + 5A = 475   25t + 5A = 475   =) 5t + A = 95   Now, using option analysis   a) t = 10 =) 5 x 10 + A = 95 =) A = 45 (not possible from (1))   b) t = 14 =) 5 x 14 + A = 95 =) A = 25 (not possible from (1) as B can’t be zero)   c) t = 16 =) 5 x 16 + A = 95 =) A = 15   16 hORRE16 hT ANSWER 16 h
<result>C</result>
A cistern of 475 litres is completely filled using pipes A and B, with Pipe A being open for 5 more hours than pipe B. If we are to interchange the operating hours of the two pipes than pipe A would have pumped half the water as much as pipe B, then find the time for which pipe B was open. Also, given that if the two pipes were open simultaneously the tank would fill in 19 hours.