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.
Q-1> A man covers a distance of 810 meter in 1 min 30 seconds. Find his speed in km/hr.
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.
Time = 9 hours
Distance = 810 kilometer
Speed = 810/9 = 90 km/hr
Now, Speed in m/sec
90 × 5/18 = 25 m/sec (Ans.)