How to work out mechanical advantage of different arrangements of hydraulic cylinders I'm hoping you can help as I've having real trouble wrapping my beleaguered brain around this. If this question is better asked on another SE just let me know. Apologies if it's a bit pedestrian ;)
I'm trying to work out how to calculate the mechanical advantage for a number of different brake setups on cars. These systems work with a simple master/slave hydraulic system. The only real complication comes in the configuration of the master cylinder.
There are 3 common types of master cylinder (simplified as best I can):


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*A single piston master cylinder feeding 2 slave cylinders.

*A dual master cylinder setup with two discreet systems of a master and a slave connected by a bar at the input of the master cylinder (so the force applied is split between each discreet system equally).

*A tandem setup where a single bore houses two cylinders in-line, each feeding a slave cylinder. The first piston has force exerted on it, and the second floating piston is moved by the pressure applied from the first piston.


If all the slave cylinders are equal (lets say 20mm), and the fluid is incompressible, what are the respective mechanical advantages of the following systems:


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*A single master cylinder of 10mm diameter, arranged as a single setup above.

*Two master cylinders of 5mm diameter, arranged as a dual setup above.

*A tandem master cylinder of 5mm diameter, arranged as a tandem setup above.


The first two I think I've got right. The mechanical advantage for number 1 should be 40:10 = 4:1. Number 2 should also be 4:1 (20:5).
The Question 
Am I right in saying that the mechanical advantage of number 3 should be 4:1 as well?
 A: Assuming that by a mechanical advantage you mean the ratio between the total force applied to all slave cylinders to the total force applied to all master cylinders, all three configuration have to be reviewed.
Taking into account that, in the static case (i.e., when nothing is moving), the pressure acting on all cylinders in contact with the same fluid is the same, the ratio of forces should be equal to the ratio of cylinder (or piston) areas, not cylinder diameters.
For instance, in the first configuration, the ratio between the combined area of the two slave cylinders and the area of the master cylinder and, therefore, the mechanical advantage, is $16:1$, not $4:1$. 
In a tandem master cylinder, the pressure associated with both pistons is the same. This is because for the floating piston to be in balance, the pressure in front of it and behind it should be the same. Since, both pistons have the same diameter, the forces associated with them should be the same as well.
If you take this and the rule about the ratio into account, finding the mechanical advantage for the tandem configuration should not be difficult.  
