48 is the scale factor!
1 foot = 12
4 feet = 48 inches
1 in. to 4 feet(or 48 in.) = 48 scale factor!
Other examples:
1: scale factor of 2 in = 4 in = scale factor of 2
2: scale factor of 20 mm = 8 cm = scale factor of 4
3: scale factor of 3 ft = 5 m = scale factor of 5
Hope this helps!
