दो पाइप क्रमशः 30 घंटे और 40 घंटे में एक टैंक को भर सकते हैं। यदि दोनों पाइपों को एक साथ खोल दिया जाए, तो टैंक को भरने में कितना समय लगेगा?

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?