A person can complete a journey in 21 hours. He covers the first one-third of the journey at a speed of 40 km/h and the remaining distance at a speed of 60 km/h. What is the total distance of his journey?

P takes 6 hours more than Q to walk 'm' km. If P doubles his speed, then he can make it in 2 hours less than Q. How much time (in hours) does P require to walk 'm' km?

A policeman spots a thief from a distance of 105 metres. The thief and the policeman travel at speeds of 90 km/h and 100 km/h respectively. How long will it take the policeman to catch the thief?