Is mechanical advantage given by : (length of effort arm)/(length of resistance arm) or (length of resistance arm)/(length or effort arm)?

Simple machines that include the lever, pulley, screw,
etc. are used to increase the force or torque that is applied. The ratio of the output
force or torque and the input force or torque is greater than 1 and is defined as the
mechanical advantage of the simple machine.

There are many
types of levers; the variation is in the location of the fulcrum, where the load is
applied and where the load is placed. In all kinds of levers the mechanical advantage is
equal to the distance over which the effort is applied to the distance over which the
load is moved. By using a lever it becomes possible to apply a small force over a large
distance and the result is a very large force acting for a small distance on the
load.