Chemistry Help!!!!!!

<p>Percent Dissociation Question </p>

<p>Please help!!!!!!!!!!!!!!!!</p>

<p>A very careful measuremnet showed that a 0.100 molality of potassium sulfate has a freezing point of -0.4315 degree Celcius. What is the percent dissociation of the potassium sulfate in this solution? (water f.d. = 1.86)</p>

<p>Answer: 66%</p>

<p>How do you get to there?</p>

<p>My answer is 77.33% am I am pretty sure I am right, but how is 66% the answer? Any confirmation or explanation?</p>