Chapter 2 Probability - 2.3 The Probability Function - Questions - Page 31: 18

$\frac{351}{400}=0.8775$

Let $P(A)=\frac{1}{10}, P(B)=\frac{1}{30}, P(A\cap B)=0.0025=\frac{1}{400}$. The probability that she is arrested for any of the two reasons is: $P(A\cup B)=P(A)+P(B)-P(A\cap B)=\frac{1}{10}+\frac{1}{40}-\frac{1}{400}=\frac{49}{400}$ Thus Lucy's chances of avoiding incarceration is: $1-P(A\cup B)=\frac{351}{400}=0.8775$