First half distance is covered by speed 4 m/s
so the time taken by the jogger to complete the distance
[tex]t = \frac{2500}{4}[/tex]
[tex]t = 625 s[/tex]
next half distance is covered by speed 2 m/s
so the time taken by it to cover the distance
[tex]t = \frac{2500}{2}[/tex]
[tex]t = 1250 s[/tex]
now the total time of the journey
[tex]T = 1250 + 625 = 1875 s[/tex]
now the average speed is given by
[tex]v = \frac{D}{T}[/tex]
[tex]v = \frac{5000}{1875}[/tex]
[tex] v = 2.67 m/s[/tex]
so its average speed will be 2.67 m/s