If we apply voltage to the series of resistors, it will get divided between top and bottom resistors. We can calculate the voltage drop using equation:
V_out = V_in*(R_bottom/R_total)
where:
V_in is voltage applied to top resistor
V_out is voltage between resistors
R_top is resistance of top resistor
R_ bottom is resistance of bottom resistor (or sum of bottom resistors if there's more than one)
R_total is sum of R_top and R_bottom
