Question

Akshil drove his car with speed of 20km per hour while going to his college . When he returned to his home along the same route, the speed of the car is 30 km per hour . Calculate the average speed of the car during tge entire journey

Answer 1

Use just the rule (2ab/a+b) where a=initial speed, b=final speed.

Answer 2

Let the distance..

Time going to the college = t1 = s/30km/ hr

Time coming from  the college =t2 = s/20 km/hr

Total time taken = t1 + t2 =t = ( s/30) + (s/20)

Total distance travelled = 2s

Average speed = Total distance /total time

                             =    2s/ [ ( s/30) + (s/20)]

                              = 2 / (1/12)

                            = 24km/hr