Two taps can separately fill a cistern 10 minutes and 15 minutes respectively and when the waste pipe is open, they can together fill it in 15 minutes. The waste pipe can empty the full cistern in?	Pick one: A) A)7 B) B)6 C) C)8 D) D)10 E) E)5
1/10 + 1/15 - 1/x = 1/15   x = 10   Answer:10
<result>D</result>
Two taps can separately fill a cistern 10 minutes and 15 minutes respectively and when the waste pipe is open, they can together fill it in 15 minutes. The waste pipe can empty the full cistern in?