# S1 Help!Watch

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#1
If A and B are two events and P(A) = 0.6, P(B) = 0.3 and P(A U B)=0.8, find:

(a) P( A n B)
(b) P( A' n B)
(c) P (A n B')
(d) P (A' n B')
(e) P (A U B')
(f) P (A' U B)

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#2
Anyone?
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#3
....
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14 years ago
#4
If A and B are two events and P(A) = 0.6, P(B) = 0.3 and P(A U B)=0.8, find:

(a) P( A n B)
(b) P( A' n B)
(c) P (A n B')
(d) P (A' n B')
(e) P (A U B')
(f) P (A' U B)

a) probability of A and B = 0.6 x 0.3
b) probability of B but not A = 0.4 (1-0.6) x 0.3
c) probability of A but not B = 0.6 x 0.7
d) probability of not A & not B = 0.4 x 0.7
e) probability of A or Not B = 0.6 + 0.7
f) probability of Not A or B = 0.4 + 0.3

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#5
htanks BUT answers in the book:

0.1
0.2
0.5
0.2
0.8
0.5
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14 years ago
#6
mmh thats odd. The rules are correct, maybe i did something wrong...

Is "If A and B are two events and P(A) = 0.6, P(B) = 0.3 and P(A U B)=0.8, find" correct"?

P(A U B)=0.8 - means probability of A union B ~ P(A) or P(B) which is P(A) + P(B)
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14 years ago
#7
(Original post by nas7232)
If A and B are two events and P(A) = 0.6, P(B) = 0.3 and P(A U B)=0.8, find:

(a) P( A n B)
(b) P( A' n B)
(c) P (A n B')
(d) P (A' n B')
(e) P (A U B')
(f) P (A' U B)

a) probability of A and B = 0.6 x 0.3
b) probability of B but not A = 0.4 (1-0.6) x 0.3
c) probability of A but not B = 0.6 x 0.7
d) probability of not A & not B = 0.4 x 0.7
e) probability of A or Not B = 0.6 + 0.7
f) probability of Not A or B = 0.4 + 0.3

the first one you can just use the addition rule..e.g.

0.8 = 0.6 +0.3 - p(A n B)
Therefore P(A n B) = 0.1
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14 years ago
#8
Isn't it P( A n B) which means A and B ~ A X B
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14 years ago
#9
(Original post by nas7232)
Isn't it P( A n B) which means A and B ~ A X B
no lol. Do you do stats modules?
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14 years ago
#10
Yeah i got a B for s1

Repeating this year to try n get near 100%

Haven't done stats in a while, i scheduled revision for april ish.

Whats the "lol" for, that's not very nice issit.

..looked in my edexcel book; got signs mixed up. Ignore the answers
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14 years ago
#11
It was a friendly lol.
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14 years ago
#12
Use a Venn diagram.

P(A n B) = P(A) + P(B) - P(A u B) = 0.1
P(A' n B) = P(B) - P(A n B) = 0.2
P(A n B') = P(A) - P(A n B) = 0.5
P(A' n B') = 1 - P(A u B) = 0.2
P(A u B') = 1 - P(A' n B) = 0.8
P(A' u B) = 1 - P(A n B') = 0.5
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