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# A and B are highly truthful (they each tell the truth

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CEO
Joined: 15 Aug 2003
Posts: 3454

Kudos [?]: 917 [0], given: 781

A and B are highly truthful (they each tell the truth [#permalink]

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11 Oct 2003, 11:28
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27.A and B are highly truthful (they each tell the truth randomly
3/4 of the time. Also, A's and B's truthfulness are independent.
Suppose A and B both look out the window to see what the weather is
like. A says, "It's raining." B says, "It's raining." What is the
probability that it actually is raining.

thanks
praetorian

Kudos [?]: 917 [0], given: 781

Intern
Joined: 16 Sep 2003
Posts: 21

Kudos [?]: [0], given: 0

Location: Buffalo (NY)

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11 Oct 2003, 12:02
answer is ---- p(a) + P(b) - P(a)*P(b)
= 3/4 +3/4 -3/4*3/4
=.93

Kudos [?]: [0], given: 0

Intern
Joined: 03 May 2003
Posts: 28

Kudos [?]: 1 [0], given: 0

Re: PS : Probability ..Rain [#permalink]

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11 Oct 2003, 13:16
praetorian123 wrote:
27.A and B are highly truthful (they each tell the truth randomly
3/4 of the time. Also, A's and B's truthfulness are independent.
Suppose A and B both look out the window to see what the weather is
like. A says, "It's raining." B says, "It's raining." What is the
probability that it actually is raining.

thanks
praetorian

Also arrive at .9375 by:
1- P(both are not telling the truth) = 1 - (1/4)(1/4) =1 - 1/16 = 15/16

Kudos [?]: 1 [0], given: 0

Re: PS : Probability ..Rain   [#permalink] 11 Oct 2003, 13:16
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