My answers and the logic and assumptions behind them. I assumed an implicit "in the UK" after every question, because this is where all my knowledge comes from.

1) 1/22

Assuming roadworthy cars. Anyone who's played Motorway Snooker will know how tricky it is to get started. I estimate I'd need to see 22 cars before a white one came up.

2) 1/1*10^7

Also assuming roadworthy cars. If we included cars sitting in scrapheaps, it becomes significantly more probable.

3) 1/1000

I would assume most collisions happen within the first or last few miles of a journey, so this estimate is effectively the same as "a car trip of at least ten miles involves a collision", which is easier to work with.

4) 9/14

I'd guess nine out of every fourteen buildings is residential. Commercial and industrial buildings tend to be larger and less numerous than residential dwellings.

5) 1/7

Based on my knowledge of population distribution by age, which I'll admit isn't that great.

6) 1/90000

Assuming an average of 250,000 words a book, and two to three typos a book.

7) 1/1*10^56

A silly number for a silly event.

8) 1/27000000

71 is a very strange number of coins to have in any object you might call a purse. This was a bit of a (number of purses) * (probability of having a weird-ass number of coins) * (spread of weird-ass coins) job.

9) 25%.

It fails divisibility tests for 2, 3, 5 and 11. Divisibility by 7 isn't something I can reliably test in under ten seconds, but it doesn't look divisible by 7. That still leaves a lot of other potential prime factors, but not nearly as many.