P and Q can complete a work in 20 days and 12 days respectively. P alone started the work and Q joined him after 4 days till the completion of the work. How long did the work last?

A thief steals a car and drives it at 15 km/hr. The theft has been discovered after one hour and the owner of the car sets off in another car at 25 km/hr. When will the owner overtake the thief from the starting point?

A person travels from A to B at a speed of 40 km/hr and returns by increasing his speed by 50%. What is his average speed for both the trips?

The distance between two cities A and B is 330 km. A train starts from A at 8 a.m. and travels towards B at 60 km/hr. Another train starts from B at 9 a.m. and travels towards A at 75 km/hr. At what time do they meet?

Two boats, traveling at 5 and 10 kms per hour, head directly towards each other. They begin at a distance of 20 kms from each other. How far apart are they (in kms) one minute before they collide?

A can run 1 km in 3 min. 10 sec. and B cover the same distance in 3 min. 20 sec. By what distance can A beat B?

A 270-metre-long train running at the speed of 120 kmph crosses another train running in opposite direcion a the speed of 80 kmph in 9 secs. What is the length of the other train?

In a river flowing at 2 km/hr, a boat travels 32 km upstream and then returns downstream to the starting point. If speed in still water be 6 km/hr, find the total journey time.

If a man cycles at 10 km/hr, then he arrives at a certain place at 1 p.m. If he cycles at 15 km/hr, he will arrive at the same place at 11 a.m. At what speed must he cycle to get there at noon?

There are 5 duplicating machines in an office. The fastest of the machines makes P copies in 10 hours and the slowest of the machines makes P copies in 11 hours. If each machine makes P copies then the average time per machine cannot be