Question

A boy walks to his school at a distance of 6 kilometre with constant speed of 2.5 kilometre per hour and back with the constant speed of 4 kilometre per hour is average speed for round trip expressed in kilometre per hour is

Answer 1

Going from home to school-

Constant speed = 2.5km/h

Distance = 6km

Time taken = 6/2.5

= 2.4 hours

Going from school to home-

Constant speed = 4km/h

Distance = 6km

Time taken = 6/4

= 1.5 hours

Total time is taken in traveling = 3.9 hours

Total distance = 12km

Average speed of round-trip = 12/3.9

= 3.08 hours

Answer 2

Answer:

<s>=40/13 km/hr.....(very good one..)

Explanation:

i) total distance= 12 km(6+6)

ii)v1=2.5 km/hr and v2= 4 km/hr

from  time=distance/speed... we get t1=12/5 hr and t2=3/2 hr..,

<s>=total distance/total time=12/(t1+t2)

<s>=(12*10)/39....taking LCM of 5 and 2..,

<s>=40/13 km/hr