If you're saying that the scale is 10 cm: 1 mm then the scale will be larger than the actual object because for every 1 mm of the object it will equal 10 cm of the scale drawing.
3 feet from each end of the mantel
8 * 24 feet = 192 sq feet per 5 hours
12* 36 = 432 square feet
432 is 2.25 times the area of 192 square feet
So, it takes 5 * 2.25 = 11.25 hours
69 is the correct answer
460 divided by 100 times 15 = 69
