Time and Work FOR SSC,UPSC,APPSC for all govt Exams

Time and work Problems can be solved in Two ways


  • Percentage Method
  • LCM Method 
LCM method is easier to use so will practice by LCM method

Model-1

1.A alone can finish work in 12 days and B alone can finish the same work in 24 days. then in how many days can A and B together will finish same Work?

Ans)

             A=12 days                                                       A+B=?
             B=24 days
   
            Now take the LCM of A and B because we need find out A+B 
            So LCM of A and B is =24 it means Total work is 24 Units

             Now we can find one days work for A and B Seperately

  •             A=(Total number of units/No of Days)


                        =(24/12)
                        =2 units/day

  •            B=(Total number of units/No of Days)

                       =(12/12)
                       = 1 Unit/day
      
                So that A+B’s One day’s Work= 2+1
                                                             =3 units / Day
  •           A and B together will finish same Work=(Total no.of Units/(No.of units/day))
                                                                                  =24/3
                                                                                  =  8 Days required to complete same job                                                 

2.A and B can do a piece of Work in 12 days. While B alone can finish it in 30 days then A alone finish the work in?

Ans)

             A+B=12 days                                                       A=?
             B=30 days
   
            Now take the LCM of (A+B) and B because we need find out A 
            So LCM of A and B is =24 it means Total work is 60 Units

             Now we can find one days work for (A+B) and B Seperately

  •             A+B=(Total number of units/No of Days)

                              =(60/12)
                              =5 units/day

  •            B=(Total number of units/No of Days)

                       =(60/30)
                       = 2 Unit/day
      
                So that B’s One day’s Work= ((A+B)’s work-A’s Work)  = (5-3)
                                                             =3 units / Day
  •          B alone can finish same Work=(Total no.of Units/(No.of units/day))
                                                                                  =60/3
                                                                                  =  20 Days required to complete same job   

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