Rate Problems: Speed, Work, Pipes and Cistern Tricks and Formulas
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Time, Speed and Distance
Important Conversion Factors:
Average Speed


If the distance is constant, then average speed is given by harmonic mean of two speeds:

If the time is constant, then average speed is given by arithmetic mean of two speeds
Relative Speed
For Trains
For Boats and Streams
Time and Work
Time & Work

If A can do a piece of work in n days, then A’s 1 day’s work

If A’s 1 day’s work then A can finish the work in n days.

If A is thrice as good a workman as B, then: Ratio of work done by A and Ratio of times taken by to finish a work
Pipes & Cisterns
If a pipe can fill a tank in ‘x’ hours and another pipe can empty the full tank in ‘y’ hours then on opening both the pipes, the net part of the tank filled in 1 hour is