# Thread: Math project help. Probabilities

1. ## Math project help. Probabilities

When you leave the movie theater, an usher tells you that there were 175 girls and only 25 boys in the theatre.

A) This makes you wonder who was sitting in the row behind you (rows have 10 seats). Find the probability that the row behind was all girls, 9 girls exactly, 8 girls exactly 7 girls exactly, 6 girls exactly, and at least 6 girls.

So guys can you show me how to do 10 girls exactly and at least 6 girls. I can figure out the rest if i see how exactly this is solved.

The thing i tried for 10 girls was
175/200 X 174/199 X 173/198.... but i got 21.9 % chance for that and i felt susicious about my answer and i needed someone to confirm that i was going it right before i went forward, plus i needed help on the at least 6 girls one since i have a feeling im doing it the long way and there is a shorter way.

2. Originally Posted by evos5000
When you leave the movie theater, an usher tells you that there were 175 girls and only 25 boys in the theatre.

A) This makes you wonder who was sitting in the row behind you (rows have 10 seats). Find the probability that the row behind was all girls, 9 girls exactly, 8 girls exactly 7 girls exactly, 6 girls exactly, and at least 6 girls.

So guys can you show me how to do 10 girls exactly and at least 6 girls. I can figure out the rest if i see how exactly this is solved.

The thing i tried for 10 girls was
175/200 X 174/199 X 173/198.... but i got 21.9 % chance for that and i felt susicious about my answer and i needed someone to confirm that i was going it right before i went forward, plus i needed help on the at least 6 girls one since i have a feeling im doing it the long way and there is a shorter way.
You basically want to know the probability of a particular number of girls in a random sample of 10 chosen from a sample of 199 people. The number of girls follows a hypergeometric distribution - read this: Hypergeometric distribution - Wikipedia, the free encyclopedia

Note that you're choosing from a population of 199, NOT 200 (I assume that the 200 includes you .....) And the value of m will depend on whether you're a girl or not ....

3. im not included. Thanks for the help too! Ill post something if i get stuck again.