A car is moving on a straight road covers one third of the distance with a speed of 20 km/h and the rest with a speed of 60 km/h. The average speed of the car is

Explanation

Let s is the total distance traveled
Then, `t_(1)` = time taken to cover `(1)/(3)` distance `=(s//3)/(20) =(s"hr")/(60) and t_(2) `= time taken to cover `(2)/(3)` distance `=(2s//3)/(60) =(s hr)/(90)`
? Total time `=t=t_(1) +t_(2) =(s)/(60) +(s)/(90)=(s hr)/(36)`
Average speed `=(s)/(s//36) =36 km//hr`