Two taps can fill a tank in 12 and 18 minutes respectively. Both are kept open for 2 minutes and the first is turned off. In how many minutes more will the tank be filled ?	Choose one
A) 15 min.  B) 20 min.  C) 11 min.  D) 13 min.  E) None of these
Part filled by first tap in one min = 1⁄12th   Part filled by second tap in one min = 1⁄18th   Now, 2[1⁄12 + 1⁄18] + unfilled part = 1   ⇒ unfilled part = 13⁄18th   ∵ 1⁄18th part of tank is filled by second tap in 1 min.   ∴ 13⁄18th part of tank is filled by second tap in 1 min.   = 18 × 13⁄18 min = 13 min.   Answer 13 min.
<result>D</result>
Two taps can fill a tank in 12 and 18 minutes respectively. Both are kept open for 2 minutes and the first is turned off. In how many minutes more will the tank be filled ?