A pipe can fill a tank in 9 hours. Another pipe can empty the filled tank in 63 hours. If both the pipes are opened simultaneously, then the time (in hours) in which the tank will be two-third filled, is:
A28
B21
C14
D7
A28
B21
C14
D7
Related Questions:
A can complete % of a work in 5 days and B can complete 40% of the same work in 10 days. They work together for 5 days and then B left the work. A alone will complete the remaining work in: