Question

A person moving in straight line cover first half interval of time with speed x. then
in next half interval he divide remaining distance in two equal parts and covers them with
speed y and z respectively. Average speed of total motion is :​

Answer 1

Explanation:

Suppose total distance is 2x

 then first half is 2x traveled with 3m/s so time taken t1=32x

after it suppose it take 2t time then 

its half i.e. t with 4.5m/s so distance s1=4.5t

another half i.e. t with 7.5m/s so distance s2=7.5t

this distance s1+s2=2x or 4.5t+7.5t=12t=2x or x=6t

Average speed is v=timedistance=t1+2t4x=32x+2t4xputting x=6t we get v=4m/