Question

a car goes from a town a to another Town b with a speed of 30 km per hour and returns back to the town a with a speed of 60 km per hour what is the average speed of a car during the complete journey​

Answer 1

when car goes from town a to town b the speed is 30 km/h

when car goes from town b to town a the speed is 60 km/h

avg speed = distance travelled/time taken

v avg = s+s/t1+t2

v avg = s+s/(s/v1+s/v2)

v avg = 2s/s(1/v1+1/v2)

= 1/1(1/v1+1/v2)

= 2/(v1+v2)/v1v2

= 2v1v2/v1+v2

now,

v1=30km/h

v2=60km/h

v avg =2*30*60/30+60

=3600/90

=40 km/h

hence , the ans is 40 km/h.