A tap can fill a tank in 10 hours. After half the tank is filled three more similar taps are opened. What is the total time taken to fill the tank completely?  Choose the correct answer
A) 5 hrs 15 mins	B) 11 hrs 15 mins	C) 3 hrs 15 mins	D) 6 hrs 15 mins	E) 7 hrs 15 mins
Time taken by one tap to fill the tank = 5 hrs.   Part filled by the taps in 1 hour = 4 * 1/10 = 2/5   Remaining part = 1 - 1/2 = 1/2   2/5 : 1/2 :: 1 : x   x = 1/2 * 1 * 5/2 = 5/4 = 1 hr 15 mins   So, total time taken = 11 hrs 15 mins   ANSWER: 11 hrs 15 mins
<result>B</result>
A tap can fill a tank in 10 hours. After half the tank is filled three more similar taps are opened. What is the total time taken to fill the tank completely?