## 1. Three pipes A, B and C can fill a tank from empty to full in 30 minutes, 20 minutes, and 10 minutes respectively. When the tank is empty, all the three pipes are opened. A, B and C discharge chemical solutions P,Q and R respectively. What is the proportion of the solution R in the liquid in the tank after 3 minutes?

## 2. Pipes A and B can fill a tank in 5 and 6 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in:

## 3. A pump can fill a tank with water in 2 hours. Because of a leak, it took 2(^{1}/_{3}) hours to fill the tank. The leak can drain all the water of the tank in:

^{1}/

_{3}) hours to fill the tank. The leak can drain all the water of the tank in:

## 4. Two pipes A and B can fill a cistern in 37(^{1}/_{2}) minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:

^{1}/

_{2}) minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after: