A horse rider covers half the distance with 5 m/s speed. The remaining part of the distance was travelled with speed 10 m/s for half the time and with speed 15 m/s for the other half of the time. The mean speed of the rider averaged over the whole time of motion is m/s. The value of is ______. [2023]
(50)

In motion BC,
where and are the distances travelled with 10 m/s and 15 m/s respectively in equal time intervals each.