1) Distance = Speed × Time2) Converting Km/hr to m/sec3) Converting m/sec to Km/hr4) If ratio of speeds is a:b then the ratio of distance covered in the same time is a:b.5) If ratio of speeds is a:b then the ratio of time taken to cover the same distance is b:a.6) If half of the distance is covered at a speed of a Km/hr and the other half at a speed of b Km/hr then the average speed for the entire journey is Km/hr. (Shortcut 1) 7) If an object travels for half of the time at a speed of a Km/hr and the other half of the time at a speed of b Km/hr then the average speed for the entire journey is Km/hr. (Shortcut 2)## Read More: Problems on Trains## Download: Practice Questions on the Concept of Trains
Concept of TRAINS8) Time taken by a train of length L meters, travelling at a speed of S m/sec to cross a pole/a standing man is 9) Time taken by a train of length L meters, travelling at a speed of S m/sec to cross a platform or a standing train or a bridge of length x meters is 10) Time taken by a train of length L_{1} meters, travelling at a speed of S_{1} m/sec to cross another train of length L_{2} meters, travelling at a speed of S_{2} m/sec in the same direction is 11) Time taken by a train of length L_{1} meters, travelling at a speed of S_{1} m/sec to cross another train of length L_{2} meters, travelling at a speed of S_{2} m/sec in the opposite direction is Let S be the speed of the stream and B be the speed of the boat in still water.Concept of STREAMS12) Upstream means against the stream (Moving in the direction opposite to the stream). Speed _{upstream} = B - S13) Downstream means with the stream (Moving in the direction of the stream). Speed _{downstream} = B + S## Read More: Boats and Streams (Concept with Example)## Download: Practice Questions on Boats and Streams12) Concept of RACESStarting Point: Point from where the race starts is known as the starting point.14) Dead Heat: If all the persons contesting a race reach the finish point exactly at the same time, the race is said to be a dead heat.15) Suppose two persons A and B are contesting a race. If before the start of the race, A is at the starting point and B is ahead of A by x metres, then we say that 'A gives B, a start of x metres'.Example: If A gives B a start of 10 meters, then it means that A covers 100 metres whereas B covers (100 - 10) = 90 metres in the same time.16) Games: A game of 100, means that the person who scores 100 points first is the winner.Example: If A scores 100 points while B scores only 88 points, then we say that 'A can give B 12 points'. |