Question

for a journey A to B a boy travels with 5kmph,10kmph, 15kmph for equal time intervals and while moving from B to A he moves with speeds 5kmph,10kmph,15kmph for equal distances. find the average speed of the boy.
answer is 9kmph
want the solution​

Answer 1

Answer:

Required average speed,

=(3×40×30×15)/(40×30)+(40×15)+(30×15)

=24km/hr

Alternatively

Time taken to traveled 1/3

distance of journey with speed 40 kmph,

=1/3/40=1/120

Time taken to traveled 1/3

distance of journey with speed 30 kmph,

=1/3/30=1/90

Time taken to traveled 1/3

distance of journey with speed 15 kmph,

=1/3/15=1/45Total time taken=1/120+1/90+1/45=45/1080Average speed=Total distance traveled/Total time taken=1/45/1080=24kmph