Question

a car moves with a speed of 75 kilometre per hour and return back with certain speed .If the average speed of the car is 54 km per hour .find the returning speed and total time of its journey?

Answer 1

This question is very simple.

Average speed = Total Distance / Total Time Taken

But we have only speeds S1 and S2

S1 = 40 km/hr

S2 = 60 km/hr

So now let us assume that the distance between a and b will be 2400 km ( LCM of 40 and 60 )

D1 = 2400 km

D2 = 2400 km

Total Distance = D1 + D2 = 2400 + 2400 = 4800 km

Now

T1 = D1/S1

T1 = 2400/40 = 60 hr

T2 = D2/S2

T2 = 2400/60 = 40 hr

Total Time = T1 + T2 = 60 + 40 = 100 hr

Now

Average Speed = Total Distance / Total Time = 4800 / 100

Average Speed = 48 km/hr