Question

Harold took 5 hours to paint 3 same-sized walls. If he works at the same rate, how long will it take him to paint 18 walls of the same size?

Answer 1

If Harold took 5 hours to paint 3 walls, then he took 5/3 hours to paint one wall.
Therefore, Harold can paint one wall in 5/3 hours, so he will take (5/3)*18 = <<(5/3)*18=30>>30 hours to paint 18 walls. Answer: \boxed{30}.