PLEAS HELP 25 points 1) Two taps A and B can fill a cistern in 6 minutes and 12 minutes respectively. The tap C can empty it in 8 minutes. If the three taps are opened simultaneously, then how long will it take to fill the empty cistern.
2) A tank has two pipes A and B. A can fill the tank with water in 8 hours and B can empty it in 12 hours. If the pipe A be opened first and the pipes be opened alternatively one at a time for 1 hour each, in how many hours will the tank be filled up?
3) A and B can do a work in 16 days; B and C in 24 days. But A, B and C working together can finish it in 12 days. In what time will A and C working together finish the work?
4) A, B and C individually can do a work in 10, 12 and 15 days respectively. They start working together. But 5 days before the work is finished A leaves and B leaves 3 days before it is finished. What time is taken to finish the work?
PLS ANSWER IF ONLY YOU KNOW IT
AND CAUSE I ASKED 4 TOGETHER YOU CAN GIVE ME ONE BY ONE
PLEASE HELP ME PL​