Given: The speed of the auto-rickshaw = 28 km/h In starting the person is 70 meters ahead of auto-rickshaw. The person is 110 meters behind after 30 seconds Concept used: When we convert speed into km/h from m/sec we multiply by 18/5. Formula used: Relative speed = Total distance/Total time Calculation: After 30 second, the total distance between them = 70 + 110 = 180 m. Now the relative speed = Total distance/Total time = 180/30 = 6 m/sec Then the relative speed in km/h = 6 × (18/5) = 21.6 km/h Now relative speed = speed of auto rickshaw – speed of person ⇒ 21.6 = 28 – speed of person ⇒ speed of person = 6.4 km/h ∴ The speed of person is 6.4 km/h.