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.
there isn't an answer, you can't get the square root of negative numbers. the sqaure root of a negative number does not exist in the set of Real Numbers
