Assuming that the length of the resistance arm of a lever is 5.5 m, and the length of the effort arm is 2.25 m, what would the mechanical advantage...

The mechanical advantage of the lever is the ratio of length of the resistance or load arm to the length of the effort arm. In other words,

mechanical advantage = length of resistance arm / length of effort arm.

In this case, the length of the resistance arm is 5.5 m and the length of the effort arm is 2.25 m. Thus the mechanical advantage in this case is

5.5 / 2.25 = 2.44

Thus, the mechanical advantage in the case of this lever is 2.44. In simple words, the lever is capable of transferring 2.44 times the applied force. That is, if 1 N is applied on the effort end, a resultant output force of 2.44 N will be generated. 

Mechanical advantage of lever is thus advantageously used to lift or move heavy loads by application of relatively smaller forces.

Hope this helps.