Answer: Hello there!
We know that the model is 28 inches long, and the scale of the model is 1/48 with respect to the real plane.
Now we want to know how long is the actual plane.
If the scale of the model is 1/48, this means that 48 models are equal in length to the actual plane. Then the length of the actual plane is 48 times the length of the model, this is:
L = 48*28 inches = 1344 inches, we could change the units for others more suiting for a plane, using that 1 feet = 12 inches, then we could write the length in feet using dividing the length in inches by 12.
L =1344/12 = 112 feets.