15 workers can build a wall in 40 days. How many days will 5 workers take to build the same wall, working at the same rate?

💡 Solution & Explanation

The total work is 15 × 40 = 600 worker-days. More workers means fewer days, so divide: 600 ÷ 5 = 120 days. Multiplying instead (13.33 days) would mean more workers take longer, which cannot be right.