I may be misreading this, but what do you mean by "the ratio"? Voltage dividers don't work by the ratio of one resistor to the other. Let's take this scenario: 5v -- 10Ω -- 5Ω -- 0v, where the 10Ω resistor is R1 and the 5Ω resistor is R2.
The formula used to find the voltage at the node between the resistors is this:
Vo = Vin * R2/(R1+R2)
Therefore, using the previous values, you get:
Vo = 5v * 5Ω/(10Ω+5Ω)
Vo = 5v * 1/3
Vo = 1.66667v
The ratio of the two resistor values gives you 2:1, which is nowhere near the correct answer.
Matt
V