Question

A machine has a mechanical advantage of 4.5. What force is put out by the machine if the force applied to the machine is 800 N?

Answer 1

If the machine's mechanical advantage is 4.5, that means that

Output force = (4.5) x (Input force) .

We know the input force, and we need to find the output force.  Rather than wander around the room looking at the floor while our hair smolders, let's try putting the numbers we know into the equation I wrote up there.  OK ?

Output force = (4.5) x (Input force)

Output force = (4.5) x (800 N)

Now dooda multiplication:

Output force = 3,600 N .  

That's exactly what the question asked for.  So we're done !