S = Speed
D = Distance
T = Time taken
A man travels 200 km in 4 hours. What is the speed in which he travelled?
S = 200/4 = 50 kmph
A cat runs at a speed of 3 meter per second. How long will it take to cross 3 km?
T = D/S = 3 x 1000 / 3 = 1000 seconds
Relative speed in same direction
Two cars start from same point and travels in same direction at speeds 40kmph and 50kmph. What is the relative speed between them?
Relative speed = 50~ 40 = 10 kmph.
Relative speed in opposite direction
Two cars start from same point and travels in opposite directions at speeds 40kmph and 50kmph. What is the relative speed between them?
Relative speed = 50 + 40 = 90 kmph.
Time taken to catch a thief
A thief standing 50 away from a police starts running away from him at a speed of 2 m/s. The police suddenly starts chasing him at a speed of 3m/s. How long will the police take to catch the thief?
D = 50m
S1 = 3
S2 = 2
Time taken, T = 50/(3-2)
= 50 seconds
Time taken to meet from opposite direction
Two persons starts from their home 3km apart and walk towards each other at a speed of 2mps and 3mps. How long (in minutes) will they take to meet each other?
D = 3000m
S1 = 2mps
S2 = 3mps
T = 3000/(2+3)
= 600 seconds
Time taken in minutes = 600/60 = 10 minutes.