Work and ratio

1. Work from Days:

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

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2. Days from Work:

If A's 1 day's work =1/n, then A can finish the work in n days.

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3. Ratio:

If A is thrice as good a workman as B, then:
Ratio of work done by A and B =3:1.
Ratio of times taken by A and B to finish a work =1:3

4. If A is 'x' times as good a workman as B, then he will take(1/n)th of the time by B to do the same work.

5. A and B can do a piece of work in 'a' days and 'b' days respectively, then working together, they will take  x*y/(x+y) days to finish the work and in one day, they will finish((x+y)/x*y)th part of work.