let total distance of path is S
for first half , time taken if t
speed = distance/time
3 = S/2t
t = S/6 .............1
for second half , time taken is T ...
for first T/2 it moves with 4.5
speed = distance/time
4.5 = 2x/T
x = 4.5T/2 ...........2
for second T/2 it moves with 7.5
7.5 = 2y/T
y = 7.5T/2 ..........3
we have , x+y = S/2so
(7.5+4.5)(T/2) = S/2
T = S/12 ...............4
total time taken during its motion is T+t
Ttotal = T+t = S/12+S/6 = 3S/12=S/4
total distance = S
average speed = total distance/total time =