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don't get probability...

Q1) Pita has 12 coins in her bag.
There are three £1 coins and nine 50p coins.
She takes 3 coins from the bag at random.
Work out the probability that she takes exactly £2.50
Reply 1
Avatar for Notnek
Notnek
21
Original post by jesusjessica15
Q1) Pita has 12 coins in her bag.
There are three £1 coins and nine 50p coins.
She takes 3 coins from the bag at random.
Work out the probability that she takes exactly £2.50

What are the different ways that you can make £2.50 from 3 of those coins?

Then I recommend drawing a tree with three sets of branches (a set of branches for each coin pick) and every pair of branches will be a £1 pick or a 50p pick. Please post all your working if you get stuck.
Original post by Notnek
What are the different ways that you can make £2.50 from 3 of those coins?

Then I recommend drawing a tree with three sets of branches (a set of branches for each coin pick) and every pair of branches will be a £1 pick or a 50p pick. Please post all your working if you get stuck.


i tried drawing the tree, it doesn't make sense, how would you work it out
as Notnek said do a tree diagram. it will be without replacement.
Original post by the bear
as Notnek said do a tree diagram. it will be without replacement.

????? plz can you show me the steps and answer, that way i will know how to work it out
Reply 5
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Notnek
21
Original post by jesusjessica15
i tried drawing the tree, it doesn't make sense, how would you work it out

Please post your working. Here's what your tree should look like:

Spoiler

Original post by jesusjessica15
????? plz can you show me the steps and answer, that way i will know how to work it out


we are forbidden to give detailed help :emo:...

your diagram should look like this:

http://i.pinimg.com/236x/91/e7/50/91e7503710ba0b91ff2653c0388694c5.jpg
Original post by Notnek
Please post your working. Here's what your tree should look like:

Spoiler



so you can get it three times
Reply 8
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Notnek
21
Original post by jesusjessica15
so you can get it three times

Are you asking a question here?
Reply 9
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Notnek
21
Original post by the bear
we are forbidden to give detailed help :emo:...

Damn right :whip:
Original post by Notnek
Are you asking a question here?

no sorry....
there are three possible ways but out of how many outcomes
Reply 11
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Notnek
21
Original post by jesusjessica15
no sorry....
there are three possible ways but out of how many outcomes

Yes there are 3 ways so there are 3 paths of the probability tree that you need to fill out.

I recommend using a tree here.
Original post by Notnek
Yes there are 3 ways so there are 3 paths of the probability tree that you need to fill out.

I recommend using a tree here.


ok thank you
(3/12) * (2/11) * (9/10) *3type this in your calculator and find the answer :smile:
why do you times it by three at the end

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