Speed, Time and Distance – Important Formulas
Numerical Aptitude Notes for CSAT Paper, SSC and Competitive Exams
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Basic Formulas
- Speed = Distance/Time
- Time = Distance/Speed
- Distance = (Speed x Time).
Ratio of Speed to Ratio of Time
- If the ratio of the 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
Average Speed Formula
- Suppose a car covers a certain distance at a km/hr and an equal distance at b km/hr. The average speed for the whole journey is = 2ab/(a + b) km/hr.
km/hr to m/sec conversion
- 10 km/hr = 10 x(5/18) m/sec.
m/sec to km/hr conversion
- 10 m/sec = 10 x(18/5) km/hr.
Important Formulas for Train base Questions
- Time taken by a train of length K metres to pass an object be negligible length like a pole or standing man or an electric post is equal to the time taken by the train to cover K metres
- Time taken by a train of length K metres to pass a stationery object of length L metres is the time taken by the train to cover (K + L) metres.
- Suppose two trains or two objects bodies are moving in the same direction at S m/s and T m/s, where S > T, then their relative speed is = (S – T) m/s.
- Suppose two trains or two objects bodies are moving in opposite directions at S m/s and T m/s, then their relative speed is = (S + T) m/s.
- If two trains of length K metres and L metres are moving in opposite directions at S m/s and T m/s, then
- The time taken by the trains to cross each other = (K + L)/(S + L) sec.
- If two trains of length K metres and L metres are moving in same directions at S m/s and T m/s, then
- The time taken by the trains to cross each other = (K + L)/(S – L) sec.
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