Question

A bag contains 8 red and 4 white balls. If A, B, C draw them in succession, wat is the probability that C will get a white ball?

Answer 1

Can anyone also suggest a good book for probability?

Answer 2

first - can you write down the different ways in which C can end up drawing a white ball?
e.g. A could draw a red ball, then B could draw a red ball, then C could draw a white ball

Answer 3

yup....
then?

Answer 4

if you write those down first then, for each row, you work out the probability of that scenario happing.
then you add up the probabilities across all rows.

Answer 5

*happening

Answer 6

Is it like this\[[(8*7*4)+(4*8*3)+(8*4*3)+(4*3*2)]/(12*11*10)\]

Answer 7

yes - that looks correct

Answer 8

but its not giving me the correct answer...answer should be 7/33. is there any othere concept?

Answer 9

not that I can think of.

Answer 10

unless the question really means: A, B then C will draw a ball each. and this will continue until no balls are left. what is the probability that C has drawn a white ball?

Answer 11

yup...this is it...but then it gets even more complex....how do i get it then

Answer 12

you can then use the same method for each round of drawing

Answer 13

there must be a way of expressing this in a concise manner

Answer 14

maybe if you consider the case where C does not draw any white ball at all, and then subtract that from 1 in the end?

Answer 15

that will complicate the sum even further....pls elaborate..

Answer 16

thinking...

Answer 17

take your time....i want to learn..

Answer 18

ok - first thought is as follows:

probability that C does NOT draw a white in first round is 8/12

now we need to consider what combination of balls could be left after the first draw.

Answer 19

means in the second trial there only two white balls left...

Answer 20

so I get after first round there are either:

a) 7 Red, 2 White
b) 6 Red, 3 White
c) 5 Red, 4 White

Answer 21

now we need to consider case (a) to (c) for the second round and work out the probability of C NOT drawing a white ball

Answer 22

getting really jammed...

Answer 23

which I /think/ is as follows:

a) 7 Red, 2 White: probability of C NOT drawing a white = 7/9
b) 6 Red, 3 White: probability of C NOT drawing a white = 6/9
c) 5 Red, 4 White: probability of C NOT drawing a white = 5/9

Answer 24

do we add all this.....or multiply all of them...

Answer 25

I /think/ we will need to do this:

(8/12)( (7/9) + (6/9) + (5/9) )

Answer 26

no - that cannot be right

Answer 27

the answer is greater than one...not possible...

Answer 28

hmmm - this case is trickier than I thought - let me think about it and I'll get back to you (unless someone else solves this before I get back)

Answer 29

?

Answer 30

okkk....@asnaseer

Answer 31

@waterineyes ..can u help

Answer 32

Is the above that you have posted question??

Answer 33

yup...it will kind of u if u try with the problem..

Answer 34

Let me think..

Answer 35

I am not getting actually sorry...
But I am still trying..

Answer 36

kk

Answer 37

For A to draw a white ball
P(w) = 4/12
For B to draw a white ball
P(w0) = 3/11
For C to draw a white ball
P(w1) = 2/10
Can you proceed from here?

Answer 38

after that wat to do..?
its just one part..

Answer 39

add them

Answer 40

not possible...way off the answer-7/33

Answer 41

It is not simple as someone can think..

Answer 42

yup..