Two taps can separately fill a cistern 5 minutes and 15 minutes respectively and when the waste pipe is open, they can together fill it in 6 minutes. The waste pipe can empty the full cistern in?
Select the correct option
A) 6 B) 8 C) 10 D) 9 E) 2
1/5 + 1/15 - 1/x = 1/6   x = 10   Answer:10
<result>C</result>
Two taps can separately fill a cistern 5 minutes and 15 minutes respectively and when the waste pipe is open, they can together fill it in 6 minutes. The waste pipe can empty the full cistern in?