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# S1 question, Blue Heinmann S1 book watch

1. Heinmann Modular Mathematics (greg attwood, gill dyer, gordon skipworth)
Blue Cover with Statistics 1 written on it
Exercise 8A, pg 153, qn 15

hi can you please help me on this qn, thanx. i would have thought that this question was just a normal simple probability question, not one to do with probability distributions.
2. ...can ANYONE help me???? please, i'm really stuck!
3. i've done it...but i used a big tree diagram

if the number tested is three, there must be one good and two bad
use probabilities without replacement
There are three combinations it could be - good bad bad, bad bad good, bad good bad. If you add these together you get 2/15

For part b use the same idea
4 ways there could be 4 picked - good good bad bad, good bad good bad, bad good good bad, good bad bad good. This gives 4/15
Add this to above answer gives 6/15
Or the two bad fuses could be picked, which is 1/15
Gives a total of 7/15
4. thanx dude, u a star

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