A and B travel from X to Y at the speed of 15 km/hr and 45 km/hr respectively . If B takes \(\frac{1}{3}\) hour lesser time than A , then what is the distance between the X and Y ?

7.5 km

Ratio                    A    :    B 

                          15   :    45

 Speed                  1    :    3

 Time                    3    :    1

 ( Distance = Speed × Time , so ratio of speed and time is inverse to each other  )

According to question , 

2R = 20 minutes 

1R = 10 minutes 

3R = 30 minutes 

Distance = 15  ×  \(\frac{30}{60}\)  = 7.5 km