   SEARCH HOME Math Central Quandaries & Queries  Question from vivianne, a student: The distance from A to B is d km and that from B to C is x km. if a bus maintains an average speed of 50km/hr between A and B and 60km/hr between B and C, it takes 3 hours to travel from A to C. If it maintains 60km/hr between A and B and 50km/hr between B and C, the journey takes 8 minutes less. What is the distance from A to C via B? Vivianne,

If the bus maintains an average speed of 50 km/hr for the d kms from A to B it takes d/50 hours.

If the bus maintains an average speed of 60 km/hr for the x kms from B to C it takes x/60 hours.

This trip takes 3 hours so

d/50 + x/60 = 3 hours.

Develop a similar equation when the average speed from A to B is 60 km/hr and the average speed from B to C is 50 km/hr. Remember to express the 8 minutes in hours.

Solve the two equations for d and x.

Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.