[Matty]

This has immediate real-world implications for me, so please don't steer me wrong.

I have little interest in, or knowledge of probability, so if this is ridiculously simple please excuse.

A person is allowed to pull 4 balls out of a sack of ten without looking into the bag. He will then throw away one and only one red ball (if he pulls one out) leaving him with three balls.

Assume there are 7 black balls and 3 red balls in the sack. What are the chances that the person will end up with at least one red ball (after throwing away one). So basically, what are his chance of pulling 2 or more red balls out of the sack?

Then assume there are 6 black and 4 red in the sack.

8 black and 2 red.

Thanks.