These types of levers, the fulcrum F is in between the effort E and the load L as shown in figure. Note that the fulcrum F need not be at the mid-point between the load L and the effort E. The load and effort is works in the same direction. In general the effort arm is greater than load arm.
In fig. AB is a class I leaver, F is fulcrum. Load L is hang from the point B. and an effort E apply from the point A. here AF is effort arm and BF is the load arm. Here,
Applied Effort x Effort Arm = Mass x Load Arm
E x AF = W x BF
M.A = W/E = AF / BF
Mechanical advantage of class I lever depends on the ratio of the length of effort arm and load arm.