Pipes A and B can fill a tank in 18 hours and 24 hours, respectively, while pipe C alone can empty the full tank in 30 hours. Pipes A and B are opened together for 6 hours and then A is closed and C is opened insta ntly along with B. After the closure of pipe A, how much time (in hours) will B and C together take to fill the remaining tank completely?

Three taps A, B, and C can fill an empty tank in 30 minutes, 20 minutes, and 10 minutes respectively. When the tank is empty, all three taps are opened. Taps A, B, and C release chemical solutions P, Q, and R respectively. What is the proportion of solution R in the tank after 3 minutes?

Two inlet pipes J and T can fill a tank in 120 minutes and 144 minutes respectively. If an outlet pipe Z is opened along with them, all three pipes together fill the tank in 240 minutes. How long will pipe Z alone take to empty the full tank?