Time and Work formula and facts

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

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

3. 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

Note: If you feel third formula a bit confusion, then please check following explanation.
If your speed is 3 times than your friend, then you will be able to do three times work when your friend will able to do it 1 time. So work done ratio of you and your friend is 3:1

Also you will take 1/3 time to finish the work than your friend, so time ratio will be 1:3