Solution

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 = 1.35p days Therefore, total work = 1.35p × a units….. (2) From equation (1) and (2), we get 20b/7 = a Therefore, total work to be done = (a + b) × p = 27bp/7 units Time taken by 'B' to build the wall = 27bp/7b = 27p/7 days Therefore, required percentage = (27p/7 – p)/p} × 100 = 285.71% more time