Mr Tan drove from Town A to Town B at a constant speed of 40 km/h. He then drove back from Town B to Town A at a constant speed of 70 km/h. The total time taken for the whole journey was 5.5 h. Find the distance between the two towns.
Let T represent the time going from A to B.
The distance = rate x time ---> distance = 40·T
Since the total time was 5.5 hrs, the time returning from B to A was 5.5 - T hours.
The distance returning ---> distance = 70·(5.5 - T)
Since the distance going is the distance returning: 40·T = 70·(5.5 - T)
Solving: 40T = 385 - 70T
110T = 385
T = 3.5 hours
The distance going = 40·3.5 = 140 km
The distance returning = 70·2 = 140 km