Conditional probability question about students owning cars and bikes

Question

At a university $0.15$ students have a car on campus. The likelihood of students having both a car and a bike on campus is $0.03$. If a student has a car on campus, what is the probability that they also have a bike on campus?

Answer 1

HINT: Imagine for a moment that there are $1000$ students. $150$ of them have a car on campus. How many have both a car and a bike on campus? What fraction of those with cars is this?

Now carry out the same analysis with an unspecified number $n$ of students.

Answer 2

$0.15$ of the students have a car. $0.03$ have a car and a bike. This means $0.12$ have a car but not a bike. Now you want the probability that they have a bike given that they have a car.

That would be:

$$\mathbb{P}\{B|C\}=\frac{\mathbb{P}\{C,B\}}{\mathbb{P}\{C\}}=\frac{0.03}{0.15}=0.2$$

Answer 3

If there are $100$ students in the campus, $15$ have a car and $3$ have both a car and a bike. Now, if I lie in the $15$ students batch, that means that $3$ of us must have both. The probability of each one of us having a bike is equal.

So according to me it must be $1/15$.