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# Need help with S1 question watch

1. Events J and K are independant events, where P(J)=0.7 and P(K)=0.1
So far I've found

P(J K) = 0.07
P(J∪ K)= 0.73

Now I'm stuck on this question "If L is event that neither J or K occurs, find P(L l K' )
So I did 1 - 0.73 Which gave me 0.27, so I assume this is L.

Then I tried to use P(L l K' )= P(L
∩ K' ) / P( K' )
And I did 0.27x0.9=0.243 to get the value of
P(L ∩ K' )
However the book says this is wrong, but I just can't get my head around it why, surely The area of J that isn't intercepting with K, is also part of K', but my book is saying P(L)=
P(L ∩ K' ) and I just don't know why.
Help greatly appreciated. :P
2. (Original post by Mikenchi)
Events J and K are independant events, where P(J)=0.7 and P(K)=0.1
So far I've found

P(J K) = 0.07
P(J∪ K)= 0.73

Now I'm stuck on this question "If L is event that neither J or K occurs, find P(L l K' )
So I did 1 - 0.73 Which gave me 0.27, so I assume this is L.

Then I tried to use P(L l K' )= P(L
∩ K' ) / P( K' )
And I did 0.27x0.9=0.243 to get the value of
P(L ∩ K' )
However the book says this is wrong, but I just can't get my head around it why, surely The area of J that isn't intercepting with K, is also part of K', but my book is saying P(L)=
P(L ∩ K' ) and I just don't know why.
Help greatly appreciated. :P
since if you look at it it is saying probabiltiy of L intersect not K, well L is an event that strictly goes against intersecting J or K ''the event that neither J or K occurs'' so the probability of them intersecting not k is simply the
3. (Original post by Robbie242)
since if you look at it it is saying probabiltiy of L intersect not K, well L is an event that strictly goes against intersecting J or K ''the event that neither J or K occurs'' so the probability of them intersecting not k is simply the
Ah I see! Reworded that makes a lot more sense, I get it now, I can finally move on! Thank you so much for your help. :P
4. (Original post by Mikenchi)
Ah I see! Reworded that makes a lot more sense, I get it now, I can finally move on! Thank you so much for your help. :P
No problem, and yeah with probability they really do try to trick you with these questions, so I can understand why you needed help in the first place

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