Huge percentage of wrong answer

Hi,
I am following the two month plan. I have been keeping record of the percentage of my wrong answers while practicing quant from Manhattan 5lb. I got wrong answers of 40.9% questions on probability and 28% on normal distribution. I was doing pretty good on the previous chapters. But these two chapters really weakened my confidence though I am not that bad at quant. What to do in this situation? Any suggestion will be appreciated. Thanks!