help! probability question! probably combination problem!

[knj9404]

alright here's how it goes

there are 37 marbles in a box
3 of those 37 marbles are black marbles

what is the probability of a person taking out 5 marbles and one of those 5 marbles is a black marble?


my brain is about to burst
help plz

 

[pka]

there are 37 marbles in a box
3 of those 37 marbles are black marbles
what is the probability of a person taking out 5 marbles and one of those 5 marbles is a black marble?

The probability that none of the five is black is $\displaystyle \dfrac{\binom{34}{5}}{\binom{37}{5}}$.
So what is the probability that at least one of the five is black?

 

[knj9404]

to Pka

i think the problem is asking the probability when only one of the 5 marbles is black..

 

[soroban]

Hello, knj9404!

The problem should have been given more precisely.
I will guess what you intended . . .

There are 37 marbles in a box: 3 of them are black marbles.
Five marbles are drawn out at random without replacement.
What is the probability that exactly one of those 5 marbles is black?

There are: .$\displaystyle _{37}C_5$ possible outcomes.

There are: .$\displaystyle \left(_3C_1\right)\left(_{34}C_4\right)$ outcomes with exactly one black marble.

$\displaystyle P(\text{exactly 1 black marble}) \;=\;\dfrac{139,\!128}{356,\!643} \;=\;\dfrac{248}{777}$

 

[knj9404]

Thank you Soroban!

your explanation helped a lot!
i think i get it now!

thank you so much for clear explanation!

 

[pka]

i think the problem is asking the probability when only one of the 5 marbles is black..

Look at the OP.oes

there are 37 marbles in a box
3 of those 37 marbles are black marbles

Where in the OP statement does it say or even imply only one?
It does not!
The selection $\displaystyle B.~B,~R$ contains a black ball.

 

[knj9404]

now i am confused pka

so what you are trying to tell me is that the question is elusive?
i think the question asks the possibility of one black marble in the 5 marbles that were drawn out of the box...

do you think it has a different solution to it?

 

[pka]

so what you are trying to tell me is that the question is elusive?
i think the question asks the possibility of one black marble in the 5 marbles that were drawn out of the box...
do you think it has a different solution to it?

This is a simple matter of reading the English Language.
Suppose that we have a bin containing six black balls and five white balls.
Let's say that I reach in and get a handful of four balls.
The question is "do you have a black ball in hand"?

I have $\displaystyle w,w,w,b$ so yes.

I have $\displaystyle w,w,b,b$ so yes.

I have $\displaystyle w,b,b,b$ so yes.

I have $\displaystyle b,b,b,b$ so yes.

I have $\displaystyle w,w,w,w$ so no!.

What is your problem with the English Language?

 

[knj9404]

To pka

So the answer is still going to be 248/777?
because the question specifically does ask for a 'single' black ball