To find the length of the dining room using the information provided you will need to understand that when you use scales with dimensions, you will apply the factor to both dimensions. Because the area is 900 times bigger this means the dimensions (each side length) were 30 times bigger (30 x 30 = 900).
If the original length was 4 inches, then the actual length is 4 x 30 or 120 inches or 10 feet.
The length of the dining room is 10 feet.
