TIME AND WORK

IMPORTANT FACTS AND FORMULAE

                                      

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

    * The ratio of time and efficiency of workers is inversely proportional to each other

     > if A is twice as good a workman  B than  

      RATIO OF WORK  OF A and B =2:1

AND the RATIO of EFFICIENCY of A &B =1:2

FOR doing speedy calculation we generally take L.C.M of time taken by workers to complete the given work in the form of total work.

Let us see and clearly understand with examples-

ques1.   R takes 5 hours to do a work.P takes 10 hours to do the same work.How long should it take to both R&P working together independently,to do same job ?

SOLUTION 

HERE we will take lcm of both 5&10 to find total work which is 10 

  R(5)                                              2 unit in 1 hr 

                     total work(10)                                          [here we divided total work with time to find                                                                                                efficiency of R& P]

  P(10)                                             1 unit in 1 hr

Again to find total time taken by P&R to complete same work together,

use formula; T.T =  T.W/EFFICIENCY

   

          =>    10/1+2 =10/3

  TOTAL TIME(T.T)=3 1/3                         ANSWER