Question

in a survey of a town, 56% of residents own a car, 21% of residents owns a truck, and 4% of residents own both a car and a truck. what is the conditional probability that a person who owns a car also owns a truck?

Answer 1

I think the answer is 15% I might be wrong tho... hehe...

Answer 2

define two events $A=\{owns \; a\; car\},B=\{owns \; a\; truck\}$.

From the information given,

$P(A)=\frac{56}{100}=0.56 \\ P(B)=\frac{21}{100}=0.21\\ P(AB)=\frac{4}{100}=0.04$

The conditional probability,

a person owns a truck given the person who owns a car is

$P(B|A)=\frac{P(AB)}{P(A)} \\ P(B|A)=\frac{0.04}{0.56} \\ P(B|A)=0.071$