Probability in different time frames

Hi all,
May I verify if my thinking is spot on [I've exhausted the ideas, and this is the best I can come up with :O]?

Thank you in advance for any assistance!

If the chances of seeing a meteor outside within an hour are 84%, what is the chance of seeing at least one new meteor outside in 30 minutes?

P(see meteor at least once within hr) = 1 - [P(seeing none in 30 min)]^2
= 1 - $\sqrt{1 - 0.84}$
= 0.6

and

If the probability of observing a car in 20 minutes is 609/625, What is the probability of observing at least one car in five minutes?

P(at least one car in 20 minutes) = 1 - [P(no cars in 5 minutes)]^4
=1 - $\sqrt[4]{[1 - \frac{609}{625}]}$
= $1 - \frac{2}{5}$