Important Quantiative aptitude formulas- time and work

Important Formulas - Time and Work

• If A can do a piece of work in n days, work done by A in 1 day = 1/n


• If A does 1/n work in a day, A can finish the work in n days


• If M1 men can do W1 work in D1 days working H1 hours per day and M2 men can do W2 work in D2 days working H2 hours per day (where all men work at the same rate), then
  M1 D1 H1 / W1 = M2 D2 H2 / W2


• If A can do a piece of work in p days and B can do the same in q days, A and B together can finish it in pq / (p+q) days
•   If A, B and C can do a work in X, Y and Z days respectively then all of them working together can finish work in
  


• If A is thrice as good as B in work, then
  Ratio of work done by A and B = 3 : 1
  Ratio of time taken to finish a work by A and B = 1 : 3
• Assuming that all men work with same efficiency, we can conclude that if the work done is constant then the number of days is inversely proportional to the number of men working. 
• 
  Thus we obtain a relationship 
  
  
  
  If work is not constant then it is directly proportional to both number of men and number of days 
  
  Where MD is equivalent to number of man days. 

  9. If A and B working together, can finish a piece of work in x days, B and C in y days, C and A in z days, then 

• A, B and C working together will complete the job in 
• A alone will complete the job in 
•  C alone will complete the job in 

 10. If A can complete a work in x days and B is k times efficient than A, then the time taken by both A and B, working together to complete the work is 

11.  If A and B, working together, can complete a work in x days and B is k times efficient than A, then the time taken by – 

           A working alone to complete the work in 

→ (k + 1) x

           B working alone to complete the work is 

12.  If A working alone takes ‘a’ days more than A and B, and B working alone takes ‘b’ days more than A and B together, then the number of days taken by A and B, working together, to finish a job is given by

13. If A can complete a/b part of work in X days, then c/d part of the work will be done in

14. If ‘a’ men and ‘b’ women can do a piece of work in ‘n’ days,then ‘c’ men and ‘d’ women can do the work in