A man covers a certain distance on a toy train. Had the train moved 4 km/hr faster, it would have taken 30 minutes less. If it moved 2 km/hr slower, it would taken 20 minutes more. Find the distance.

Machine A, working alone at its constant rate, produces x pounds of peanut butter in 12 minutes. Machine B, working alone at its constant rate, produces x pounds of peanut butter in 18 minutes. How many minutes will it take machines A and B, working simultaneously at their respective constant rates, to produce x pounds of peanut butter?

Tow trains running at the rate of 75km and 60km an hour respectively on parallel rails in opposites directions, are to pass each other in 8 seconds and when they are running in the same direction at the same rates as before, a person sitting in the faster train observes that he passes the other in 33$\frac{1}{2}$ seconds. Find the lengths of the trains.

pot contains 81 litres of pure milk $\frac{1}{3}$ of liters of the milk is replaced by the same amount of water. Again $\frac{1}{3}$ of the mixture is replaced by that amount of water. Find the ratio of milk and water in the new mixture.

A train 400 meter long overtook a man walking along the line in the same direction at a speed of 5 km/hr and passed him in 40 seconds. The train reached the station in 20 minutes after it had passed the man. In what time did the man reach the station?