Important Facts and Formulas ( Time and Distance )

  • Speed = (Distance / Time)
  • Distance = Time × Speed
  • Time = Distance / Speed
  • When we need to change x km/hr to m/sec, then multiply it by 5/18

x km/hr = (5 × x)/18 m/sec

  • When we need to change x m/sec to km/hr, then multiply it by 18/5

x m/sec = (18 × x)/5 km/hr

  • If the ratio of speeds of A and B is a : b, then the ratio of the times taken by them to cover the same distance is (1/a) : (1/b) or b : a.
  • In fact there exists an inverse relation between distance and time.

Examples

Q-1> A man covers a distance of 810 meter in 1 min 30 seconds. Find his speed in km/hr.

Solution-

Time = 1 min 30 seconds = 90 seconds

Distance = 810 metre

Speed = 810/90 = 9 m/s

Now, Speed in km/hr

9 × 18/5 = 32.4 km/hr (Ans.)

Q-2> A train covers a distance of 810 km in 9 hours. Find the speed in m/sec.

Solution-

Time = 9 hours

Distance = 810 kilometer

Speed = 810/9 = 90 km/hr

Now, Speed in m/sec

90 × 5/18 = 25 m/sec (Ans.)

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