A can do a piece of work in 15 days and the efficiency of B and C is 12 unit/day and 10 unit/day respectively. Work done by A and C together in 1 day is 4 units more than B and C together. Then find the time taken by B is how much percent more than time taken by A?

33\(\frac{1}{3}\)%

                              B          C

          Efficiency      12         10

ATQ,

        (A+C) - (B+C) = 4

          A - B = 4     (A's eff. is 4 unit more than B's)

Hence,

                                           A               B

        efficiency                     16             12

Time taken by A & B             12             16

 Total work = Efficiency × Number of days

So ratio of efficiency and time is inverse to each other 

Now, more time is taken by B i.e 4R

    Required %  = \(\frac{4R}{12R}\) × 100 = 33\(\frac{1}{3}\)%