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Probability and Time Distance Question

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Probability and Time Distance Question [#permalink]

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New post 19 Jul 2009, 18:39
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A
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Hi Everyone,

Please find attached the document having questions for probability and time distance.

Thanks in advance.

Regards,
Aban
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Kudos [?]: 2 [0], given: 0

Senior Manager
Senior Manager
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Joined: 23 Jun 2009
Posts: 357

Kudos [?]: 136 [0], given: 80

Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago
Re: Probability and Time Distance Question [#permalink]

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New post 20 Jul 2009, 00:52
For q1;

The total time is = time traveled 60 mph + time traveled 30 mph.
(x-5)/60 hours + 5/30 hours = (x+5)/60 hours.
if he had traveled at a constant 60 mph speed. His travel time would have been x/60 hours.
Thus we get the percentage =>
Time difference = (x+5)/60-x/60= 5/60 hours = 1/12 hours.
Time for constant travel = x/60 hours.
So the percentage difference is (1/12).100 / (x/60)= 5.100/x = 500/x %

Kudos [?]: 136 [0], given: 80

Senior Manager
Senior Manager
avatar
Joined: 23 Jun 2009
Posts: 357

Kudos [?]: 136 [0], given: 80

Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago
Re: Probability and Time Distance Question [#permalink]

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New post 20 Jul 2009, 00:56
For question 2;
There are 4 cases;
1- St.A plays good
2- St.A plays bad but st.B plays good
3- St.A and St.B plays bad but st.C plays good.
4-All plays bad.
Prob of 1st case is 0,3
Prob of 2nd case is 0,7.0,3
Prob of 3rd case is 0,7.0,7.0,3
Prob of 4th case is 0,7.0,7.0,7
Sum of all is 0,3 + 0,21 + 0,147 + 0,343 = 1
In only the last case the song is bad. So the prob. that a good song is played is 1-0,343=0,657
D

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Re: Probability and Time Distance Question [#permalink]

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New post 20 Jul 2009, 02:24
For everyone's benefit
Q1
Image

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Re: Probability and Time Distance Question [#permalink]

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New post 20 Jul 2009, 02:26
Q2
Image

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Re: Probability and Time Distance Question [#permalink]

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New post 20 Jul 2009, 02:31
Q2)
Prob of Leo to hear a song he likes =
Prob of Radio A playing songs which Leo likes
+Prob of Radio B playing songs which Leo likes
+Prob of Radio C playing songs which Leo likes
= 0.3 + 0.3 * 0.7 +0.3 *0.3 *0.7
= 0.3+0.21+0.147
=0.657
Option D

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Manager
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Joined: 27 Jun 2008
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Kudos [?]: 34 [0], given: 11

Re: Probability and Time Distance Question [#permalink]

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New post 20 Jul 2009, 02:39
Time spent with 5 mile@30mph = X-5/60 + 5/30 = (X+5)/60
Time spent with entire trip @60mph = X/60.
Time Diff = 1/12
Q: % of diff with total time @60mph:
(1/12) / (X/60)*100
= (500/X)%

Kudos [?]: 34 [0], given: 11

Intern
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Re: Probability and Time Distance Question [#permalink]

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New post 20 Jul 2009, 18:17
Hi Guys,

Time distance was so simple... i just screwed it ... dont know y ... thanks for that one .. but for the probability one can anyone please elaborate the below mentioned logic for me as i dont know much about the proability:

1. Radio A --> 0.3 (I understand)
2. Radio B --> 0.3 (For radio B) * 0.7 (for the case where radio A is not played)
3. Radio C --> 0.3 (For radio C) * 0.3 (Why this 0.3 and not 1 - 0.3 = 0.7) * 0.7.

I dont understand the logi behind two times 0.3 in the last case as mentioned by irajeevsingh.

i know it might b simple... not clicking to me :( :( ....

Thanks for your help.

Regards,
Aban

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Senior Manager
Senior Manager
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Joined: 23 Jun 2009
Posts: 357

Kudos [?]: 136 [0], given: 80

Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago
Re: Probability and Time Distance Question [#permalink]

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New post 20 Jul 2009, 23:11
Look at this file. This problem is a decision tree problem.
Attachments

dectree.JPG
dectree.JPG [ 13.3 KiB | Viewed 1113 times ]

Kudos [?]: 136 [0], given: 80

Re: Probability and Time Distance Question   [#permalink] 20 Jul 2009, 23:11
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