Ramesh walks a certain distance and rides back in a total time of 5 hours 45 minutes. If he could ride both ways in 3 hours 30 minutes, find the time required by him to walk both ways.

Rohan walks around a circular field at the rate of 1 round per hour while Shreyas runs around it at the rate of 5 rounds per hour. They start in the same direction from the same point at 8:30 AM. When will they first cross each other?

In covering 90 km, R takes 4 hours more than S. If R triples his speed, then he would take 2 hours less than S. What is R's original speed (in km/h)?