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S1 tree diagrams.

Stuck on this question. I've done the first part of the tree but I can't seem to do the second part of it.

Question below ImageUploadedByStudent Room1392993963.177756.jpg


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Reply 1
Avatar for TenOfThem
TenOfThem
18
Original post by zed963
stuck on this question. I've done the first part of the tree but i can't seem to do the second part of it.

Question below ImageUploadedByStudent Room1392993963.177756.jpg


posted from tsr mobile


p(bg) + p(gb)
Reply 2
Avatar for zed963
zed963
OP
16
Original post by TenOfThem
p(bg) + p(gb)


Yes that is correct for part b but I can't construct the tree diagram properly.

Why is the second part of the tree diagram 1/3?
Original post by zed963
Yes that is correct for part b but I can't construct the tree diagram properly.

Why is the second part of the tree diagram 1/3?


For second part of tree
If you first draw a red then for the second draw you can have red,blue or green with equal probability since there is 1 of each left, but if you first draw blue then on the second draw you can only get red or green (drawing now from 2 red and 1 green.
Similar argument if first drawn is green.
Reply 4
Avatar for zed963
zed963
OP
16
Original post by brianeverit
For second part of tree
If you first draw a red then for the second draw you can have red,blue or green with equal probability since there is 1 of each left, but if you first draw blue then on the second draw you can only get red or green (drawing now from 2 red and 1 green.
Similar argument if first drawn is green.


How do you know that the person hasn't taken out 2 reds?
Original post by zed963
How do you know that the person hasn't taken out 2 reds?


He can take two reds.
Here is the tree diasgram.
Tree Diagram.jpg24.0KB
Reply 6
Avatar for zed963
zed963
OP
16
Original post by brianeverit
He can take two reds.
Here is the tree diasgram.


So if they take two reds and then they won't have any left. So why is the probability of picking red again a third?
Reply 7
Avatar for AKell17
AKell17
12
Original post by zed963
So if they take two reds and then they won't have any left. So why is the probability of picking red again a third?


It isn't... It's saying the possibility of picking a red on the second draw is a third if they picked up a red the first time
Reply 8
Avatar for zed963
zed963
OP
16
Original post by AKell17
It isn't... It's saying the possibility of picking a red on the second draw is a third if they picked up a red the first time


Wait I'm not understanding something.

So we pick two beads randomly but is this in one go or two goes?
Reply 9
Avatar for AKell17
AKell17
12
Original post by zed963
Wait I'm not understanding something.

So we pick two beads randomly but is this in one go or two goes?


You pick one up, and put it aside
You pick a second one up, put it aside
Reply 10
Avatar for zed963
zed963
OP
16
Original post by AKell17
You pick one up, and put it aside
You pick a second one up, put it aside


Makes sense.

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