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# s1 question help watch

1. a bag contains 40 plastic tiles which are used in a word game. each title has a single letter written on it. 16 of the tiles have vowels written on them and the remaining 24 tiles have consonants written on them. Tara picks 5 tiles, at random and without replacemwnt, out of the bag.

Find the probability that tara choose 2 tiles with vowels and three with consonants.

where do i start been straing at it for half an hour
2. Draw a tree diagram and remember she picks the letters without replacement
3. (Original post by AndersonsBentFoot)
Draw a tree diagram and remember she picks the letters without replacement
tried that but end up getting terribly confused.

ended up with (16/40 * 15/39) + (24/40*23/39*+22/39), which is terribly wrong i think
4. In that order? Or any order?
5. Other strategy then:

How many ways can you pick 5 tiles from 40? I assume you do 'choose' stuff.

How many ways can you choose 2 vowel-tiles from 16 vowel-tiles? And again for the other things?

And now you've got 5 tiles, in how many importantly-different ways could you arrange them?
6. the anwer is 0.369. but i dont know how do work it out. the above posts are confusing me even more
7. I'll try again:

Method (1) Tree

Choose first tile; two options - vowel or consonant; draw lines with probabilities

Choose second tile (for each branch of two). Two options for each branch. Probabilities have shifted slightly because different tiles left in bag

Choose third tile etc up to five. Label each of 32 leaves with probability. Add up the ones you want
8. Method (2) combinations.

(a) in how many different ways could you draw five tiles from 40?

(b) how many ways of drawing five tiles from 40 meet the 3/2 spec?

p = b/a
9. (Original post by ian.slater)
Method (2) combinations.

(a) in how many different ways could you draw five tiles from 40?

(b) how many ways of drawing five tiles from 40 meet the 3/2 spec?

p = b/a
cheers mte appreciate it, got there in the end. one thing that i struggle with on probabaility is that i dont know if im working it out the right way. so most of the time i have 2 work backwards by using the answer. any tips on how to solve this issue or on
s1 in general.
10. I would say that if you least attempt it even if you don't manage it your teacher can't get mad at you so just ask them to help you tomorrow
11. S1 is about learning a small list of techniques and then applying them. The list depends on your exam board. Some people just get it quickly, some people, even good mathmo's, take time to practise. Conditional probability (the probability that you can answer a question given that you have asked someone on TSR) is often hard to get. I know that sounds lame, but it's the best I can do.

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Updated: January 20, 2010
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