Question 931626
I am going to use a suffix of M to indicate dimensions of the model.

Given:
LM = 15ft
WM = 3ft
HM = 1ft
L = 12000ft
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To find the scale used you need to compare like dimensions. In this example we are given both lengths.

Find the scale of the model: {{{L/LM}}}
{{{12000/15 = 800}}}
Multiply the other model dimensions by 800 to find their actual values in real life.

W = 3ft * 800
W = 2400ft

H = 800 * 1ft
H = 800ft