I open the 1st box, there is a toy car in it.

I open the 2nd box, there is also a toy car in it.

I open the 3rd box, there is also a toy car in it.

...

I open the 9th box, there is also a toy car in it. :) wow, I got 9 toy cars in 9 boxes...

what is the probability that 10th box also has a toy car in it?

also generalize 10 to any number...

what is the probability that nth box also has a toy car in it, if all n-1 boxes each have a toy car in them.