Question

a man walks 6km to 12 km/h and returns at 10km/h.find his average speed

Answer 1

A ------------------------------- B

suppose this is the distance of 6km

from A to B
distance = 6km
speed = 12km/h
time taken = 6 /12
= 0.5 h

from B to A

distance = 6km
speed = 10km/h
time = distance/ speed
= 6/10
= 0.6 h



average speed = total distance covered/ total time taken

= (6 +6) /( 0.5 + 0.6)
= 12 /1.1
= 10.90km/h

Answer 2

Average speed = 2v1v2 / (v1 + v2)
= (2 × 12 × 10) / (12 + 10)
= 10.90 kmph

Average speed of man is 10.90 kmph