Q: 12 pens cost ₹180. Cost of 7 pens? 15 workers finish in 10 days; how long for 25 workers? Part A (direct): 1 pen = 180/12 = ₹15. 7 pens = 7 × 15 = ₹105. Part B (inverse): Total work = 15 × 10 = 150 worker-days. Days for 25 = 150/25 = 6 days.