Latest topics
» Homework list Wed Mar 23, 2011 12:26 am by Admin Tue Mar 22, 2011 9:02 pm by Admin Tue Mar 22, 2011 7:59 am by fergus

» Find k - quadratics problem Wed Mar 16, 2011 12:40 am by Admin

» S1- probability question Mon Mar 07, 2011 8:54 pm by Admin Mon Mar 07, 2011 8:31 pm by Admin

» surds problem Sun Feb 27, 2011 7:02 am by fergus

» Solving equations Mon Feb 21, 2011 7:35 pm by Admin

» Circle theorem question Sun Feb 06, 2011 2:09 am by Admin

Poll
Who is online?
In total there is 1 user online :: 0 Registered, 0 Hidden and 1 Guest

None

Most users ever online was 69 on Wed Jul 03, 2019 10:37 am

# Probability questions ## Re: Probability questions

I think the answer is 6.5
because if the probability of obtaining A is 0.5 and obtaining B is 0.35 and the probability of obtaining neither's intersection is o.2
then 0.5 - 0.2 is 0.3 and 0.35- 0.2 is 0.15
and 0.15 + 0.5 is 0.65 and 0.3+0.35 is also 0.65...................right?

## Re: Probability questions

I think that it's 0.45.
I did the same thing as Timmy, but instead I added 0.3 to 0.15.

But it could be 0.2.
Neither's intersection is the middle bit, isn't it. So it would be 0.2

So confused

## Re: Probability questions

Federico wrote:I think that it's 0.45.
I did the same thing as Timmy, but instead I added 0.3 to 0.15.

But it could be 0.2.
Neither's intersection is the middle bit, isn't it. So it would be 0.2

So confused
freddy i dont think A'∩B' is the middle section. Mr safdar wouldnt give us a question with the answer writen in front of us.
im not too sure if 0.3 to 0.15s wrong though
so i also think its 0.45

the letters in bold give off a truth

## Re: Probability questions

fergus wrote:
Federico wrote:I think that it's 0.45.
I did the same thing as Timmy, but instead I added 0.3 to 0.15.

But it could be 0.2.
Neither's intersection is the middle bit, isn't it. So it would be 0.2

So confused
freddy i dont think A'∩B' is the middle section. Mr safdar wouldnt give us a question with the answer writen in front of us.
im not too sure if 0.3 to 0.15s wrong though
so i also think its 0.45

not bad fergus but thats not a good hidden message and i think that A'∩B' is anything that is not A intersects with anything that is not B so the entire outside of both circles

we want to find where A and B both occur so what we want is the probability of A∩B however where i am having trouble finding that.

the letters in bold give off a truth

## Re: Probability questions

I think the answer is 0.05

because [p(A'∩B') = 0.2] is the probability of obtaining neither's intersection,
and we want to find p(A and B), middle section.
p(A) = 0.5 , p(B) = 0.35 , p(A'∩B') = 0.2 , and I think E = 1

E - p(A'∩B') = p(A∪B)
1 - 0.2 = 0.8 -----------------> so, p(A∪B) = 0.8

p(A∪B) = p(A) + p(B) - p(A∩B)
0.8 = 0.5 + 0.35 - p(A∩B)
∴ p(A∩B) = 0.5 + 0.35 - 0.8 = 0.05

## Well done

Well done Rachel. 0.05 is correct.

If you want to find the answer in terms of areas- the area inside the circles has to be 0.8. P(a)+P(b)=0.85 therefore we have 0.05 extra or counted twice.

## Re: Probability questions 