Let number of days taken by A alone to complete job be a days.Number of days taken by alone B to complete job = a × 125/100 = 5a/4Number of days A worked to complete half of work = 1/2 × a = a/2A's 1 day's work = 1/aB's 1 day's work = 4/5aRatio of time taken alone by A and B = 4:5(A + B)'s 1 days work = 1/a + 4/5a = 9/5a45% of work is completed in 4 days by A and B.If they work together, then work will complete in = 4 x 100/45 = 80/9⇒ 9/5a = 9/80⇒ a = 16Number of days in which B alone can complete work = 16 x 5/4 = 20 days

Unable to solve this image.png 47.78 KB

Unable to solve this image.png 47.78 KB