Time and Work -Competitive Exam Questions and Answers With ShortCuts

If you are preparing for competitive exams, one of the sure shot questions in aptitude is time and work related problems. Though the questions asked are simple, without knowing the correct methods, there is a chance of making mistakes. This guide explains various short cuts which can be used to answer the work and time related questions simply with complete solution. For those who are preparing for various government jobs through PSC and UPSC may find this guide helpful. I have solved some of the previous year Time and Work related PSC examination questions at the end of this tutorial. Some of the important concepts a student needs to know while answering Time and Work related aptitude questions are provided below.

  • If a man completes certain work in 'n' days, work done by him in one day is 1/n.

  • If the work done by a man in one day is 1/n, he can finish the total work in n days.

  • Time and work is always inversely proportional to each other.

  • If M1 persons can do W1 work in D1 days and M2 persons can do W2 work in D2 days, the general formula to find the total work or total time is :

    M1 * D1 * W2 = M1 * D2 * W1


It is important to learn the above concepts to solve Time and Work related aptitude questions. Now let us check how to solve these questions using short cuts.

Solved Examples

  1. If A can finish a specific work in 10 days and B can do the same work in 20 days. Find the time required to complete the work by both A and B together

    Ans:
    Work done in a day by A = 1/(10)
          Work don by B in a day = 1/(10)
    
         Work done in a day by both A and B together = 
    1/(10)  + 1/(20) = (2 + 1)/(20) =3/20 
     
    { Here we took the LCM of both denominators. To learn more about it,
     click the link below.
    
    L.C.M. & H.C.F. For Aptitude Questions   }
    
    Now apply the  first law provided in this tutorial to find the time needed
     to complete the work by both A and B
    
    => reverse of 3/20 => 20/3 days
    
      
  2. 40 persons make 60 bricks in 3 hours. if 8 persons leave the work, how many bricks will be made by the remaining persons in next 6 hours.

    Ans:
    Here we need to use the formula M1 * D1 * W2 = M2 * D2 * W1 
               Here M1 = 40 M2= 32 W1 = 60 D1= 3 D2= 6 W2 = ?
       
                       M2  * D2 * W1
                    ____________________
    
         W2 =        
                       M1 * D1
    
    
    =>  W2 = (32 * 6 * 60)/ (40 *3) = 96 bricks
    
    
  3. If X can do a piece of work in 25 days and Y can finish it in 20 days. They worked together for for 5 days and then X left. How many days Y will take to complete the work ?

    Ans:
    Work done by X in a day = 1/25
    Work done by Y in a day =1/20
    
    Work done by both X and Y in 5 days = 5 * (1/25 + 1/20) = 9/20  
    
    Remaining work = 1 - (9/20) =11/20
    
    Y finish 1/20 work in a day. So to finish 11/20 work, Y needs 11 more days.
    
    


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