Mohit went from Delhi to Shimla via Chandigarh by car. The distance from Delhi to Chandigarh is 3/4times the distance from Chandigarh to Shimla. The average speed from Delhi to Chandigarh was 1 and 1/2 times that from Chandigarh to Shimla. If the average speed for the entire journey was 49km/hr, what was the average speed from Chandigarh to Shimla?

Solution :
           

                    Delhi________________Chandigarh______________Shimla
Let the distance from Chandigarh to Shimla be X.km=d2
So, the distance from Delhi to Chandigarh be 3X/4.km=d1

Let the speed from Chandigarh to Shimla be y km/hr=S2
So,the speed from Delhi to Chandigarh =3/2y=S1

Let T1 be the time taken from Delhi to Chandigarh=(3x/4)/(3y/2)=1/2.x/y hrs
Let T2 be the time taken from Chandigarh to Shimla=x/y hrs
So total time of journey from Delhi to Simla=3/2xy

The total distance from Delhi to Simla=7x/4
The average speed from Delhi to Simla=(7x/4)/(3/2.x/y)
                                                               =>7y/6=49
                                                               =>y=42 km/hr(Answer)