A and B travel from X to Y at the speed of 20 km/hr and 30 km/hr respectively . If B takes \(\frac{1}{4}\) hour lesser time than A , then what is the distance between the X and Y ?

15 km

Ratio                    A    :    B 

                          20   :    30

 Speed                  2    :    3

 Time                    3    :    2

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

According to question , 

1R = 15 minutes 

3R = 45 minutes 

Distance = 20  ×  \(\frac{45}{60}\)  = 15 km