Thread: Probability for a certain event

Todays really not my day, I should know this but I'm just too unsure:

Let's say we got a chest with 30 balls in there, 25 black and 5 golden.
I want to find out the probability to get at least 1 golden ball, having 5 tries and not being allowed to put the balls back in there once I get them out.

I do know that its

1 - P(no golden balls in 5 tries)

but I'm having trouble remembering how to get my P

is it 5/30+5/29+...
or 1/25+1/24+...
or maybe 1/30+1/29+...

or even something completely different?

Thanks for your time

Originally Posted by MuhTheKuh

Todays really not my day, I should know this but I'm just too unsure:

Let's say we got a chest with 30 balls in there, 25 black and 5 golden.
I want to find out the probability to get at least 1 golden ball, having 5 tries and not being allowed to put the balls back in there once I get them out.

I do know that its

1 - P(no golden balls in 5 tries)

but I'm having trouble remembering how to get my P

is it 5/30+5/29+...
or 1/25+1/24+...
or maybe 1/30+1/29+...

or even something completely different?

Thanks for your time

Pr(at least one) = 1 - Pr(none) and Pr(none) = (25/30)(24/29) ....(21/26)