The ideal mechanical advantage (IMA) of an inclined plane is given by:
[tex]IMA = \frac{L}{h} [/tex]
where L is the length of the inclined plane while h is the height.
In our problem, L=120 m and h=40 m. Therefore, the IMA of the ski lift is
[tex]IMA= \frac{120 m}{40 m}=3 [/tex]