Question

Given pr(A)=3/5, pr(B)=1/4. Find

a) Pr(A' n B) if P(A u B)=3/4
b) Pr(A' n B)if A and B are mutually exclusive.

Can anyone help me out how should i do question b).

Thanks.

Answer 1

Did you calculate P ( A and B)
P (A U B) = P(A) +P(B) - P(A and B)

Answer 2

For a) I used 1-[A - Pr(A u B)] and i got 23/20.

Answer 3

Oh you mean this formula
P(E^c) = 1 -P(E)
that's for
P(A^c and B^c) = 1-P(A or B)

Answer 4

hmmm..

Answer 5

I'm also studying this this semester ...

Answer 6

Are you in Year 12 as well ???

Answer 7

but we know that P(A) = 3/5 and B = 1/4
and then P( A U B) = 3/4
we could use P (A U B) = P(A) +P(B) - P(A and B)
but switch the terms
P(A U B) -P(A)-P(B) = P(A and B)
3/4-3/5-1/4

Answer 8

it's called university hun

Answer 9

ohhhhh

Answer 10

danggg what I was supposed to do didn't even work . According to Axiom 1
\[0 \leq P(E) \leq 1 \] the probability of an event must be between 0 and 1. Can't exceed 1 and can't have negative numbers

Answer 11

yep!

Answer 12

so how should i do question b)

Answer 13

do you know set theory?

Answer 14

(A' and B) or (A or B) that leads to
(A' and A) or ( B or B)
empty set or (B) which becomes B

Answer 15

we need set theory to get some equations, and then we can use Axiom 3 on it

Answer 16

because the union of events becomes the sum of events
like for example
P(A U B) U P(A) by Axiom 3
P(A U B) + P(A)

Answer 17

I'm not quite sure about term Axiom 3

Answer 18

You could do a venn diagram for this