Important Formulae :
If A can do a piece of work in n days, then A's 1 day's work = 1n
If A's 1 day's work = 1n, then A can finish the work in n days.
If A is twice as good a workman as B, then
ratio of work done by A and B in the same time = 2 : 1
ratio of times taken by A and B in doing the same work = 1 : 2