Math Formulas: Time and Work

1. Work from Days:
   If A can do a piece of work in n days, then A's 1 day's work = 1/n
2. Days from Work:
   If A's 1 day's work = 1/n , then A can finish the work in n days.  
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.