A and B start at same time with speed of 40 km/hr. and 50 km/hr respectively. If in covering journey A takes 15 min longer than B, total distance of journey is :

$$\eqalign{ & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\text{ A }}:{\text{ B}} \cr & {\text{Ratio of speed = }}\,4\,\,:\,\,5 \cr & {\text{Ratio of time = }}\,\,\,\,5{\text{ }}:{\text{ }}4{\text{ }} \cr & (5 - 4){\text{ unit = 15 unit}} \cr & {\text{1 unit = 15 min}} \cr & {\text{So, time taken by B :}} \cr & {\text{ = 4}} \times {\text{15}} \cr & {\text{ = 60 min}} \cr & {\text{ = 1 hr}} \cr & {\text{Distance = S }} \times {\text{ T }} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\text{ = 50}} \times {\text{1 }} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{\text{ = 50 km}} \cr} $$