Probibility (1 Viewer)

[danger stitch]

Having a bit of trouble with this question. Can someone tell me how I do this one?

'A bag contains five blue marbles, siz red marbles and four white marbles. Marbles are drawn, one at a time without replacement, from the bag.

What is the probibility that of the first two marbles drawn one is red and one is white?'

 

[Casmira]

Blue - 5/15, Red 6/15 and White 4/15
Total marbels is 15

6/15 x 4/14

(reduces because one red is taken out so the total of marbels reduce by 1)

 

[danger stitch]

Ah shit...just realised I was doing it properly, but using the Blue and the white instead of the red and the white...
I can now calm down!!! LOL

Good luck all!

 

[Jayphen]

Blue - 5/15, Red 6/15 and White 4/15
Total marbels is 15

6/15 x 4/14

(reduces because one red is taken out so the total of marbels reduce by 1)

But the question doesn't specify which must be taken out first.. Your answer is assuming the red is first, then white..

I'm not sure of the answer myself, but the tree diagram I drew tells me it's 2/9.

I may be wrong though.

Edit: actually, I know I'm wrong, because I didn't include the probabilities in my diagram.

I think it's actually 8/35

 

[danger stitch]

Yeah true. I'm pretty sure you times the top number by two...

 

[danger stitch]

I'm 100% sure the answer is 8/35.

 

[Jayphen]

heh I wrote the wrong answer in my post - I got 8/35 aswell using the tree diagram with probabilities in it.

 

[danger stitch]

By the way, hi Jayphen!
You're the first person on here I know...

 

[Jayphen]

By the way, hi Jayphen!
You're the first person on here I know...

Hey man
Was waiting for you to say something - thought you had forgotten me hehe

 

[H.S.What?]

B B
(5/15) (5/14)
/ /
/ /
/ /
/----- R --------R
\ (6/15)\ (5/14)
\ \
\ \
\ W ----------> Red then White (6/15 x 4/14 prob.)
\ (4/14)
\ B
\ (5/14)
\ /
\ /
W------------R ------> White then Red (4/15 x 6/14 prob.)
(4/15) (6/14)
\
\
W
(3/14)

(6/15 x 4/14) + (4/15 x 6/14) = 8/35 probability of getting a white and a red, the order they are picked out is regardless.

 

[H.S.What?]

yea my tree diagram didnt post properly (grr!!!) but the answer is 8/35