The time taken by ‘A’ to build a wall alone is 20% more than the time taken by him to build it along with ‘B’. ‘B’ will take how much percent more time to build the same wall than the time taken by him to build it along with ‘A’?

Let the work ‘A’ and ‘B’, can do in 1 day be ‘a’ units and ‘b’ units, respectively. Let they takes ‘p’ days to build the wall, together Therefore, Total work = (a + b) × p units …….. (1) According to the question, Time taken by ‘A’ to build the wall alone = 1.20p days Therefore, total work = 1.20p × a units….. (2) From equation (1) and (2), we get 5b = a Therefore, total work to be done = (a + b) × p = 6bp units Time taken by 'B' to build the wall = 6bp/b = 6p days Therefore, required percentage = (6p – p)/p} × 100 = 500% more time