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# Probability and Time Distance Question

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Intern
Joined: 29 Jun 2008
Posts: 15
Probability and Time Distance Question  [#permalink]

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19 Jul 2009, 19:39
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Hi Everyone,

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

Regards,
Aban

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Time_Distance_Probability_Question.doc [106.5 KiB]

Senior Manager
Joined: 23 Jun 2009
Posts: 353
Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago
Re: Probability and Time Distance Question  [#permalink]

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20 Jul 2009, 01:52
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 %
Senior Manager
Joined: 23 Jun 2009
Posts: 353
Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago
Re: Probability and Time Distance Question  [#permalink]

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20 Jul 2009, 01:56
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.
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
Manager
Joined: 27 Jun 2008
Posts: 140
Re: Probability and Time Distance Question  [#permalink]

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20 Jul 2009, 03:24
For everyone's benefit
Q1
Manager
Joined: 27 Jun 2008
Posts: 140
Re: Probability and Time Distance Question  [#permalink]

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20 Jul 2009, 03:26
Q2
Manager
Joined: 27 Jun 2008
Posts: 140
Re: Probability and Time Distance Question  [#permalink]

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20 Jul 2009, 03:31
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
Manager
Joined: 27 Jun 2008
Posts: 140
Re: Probability and Time Distance Question  [#permalink]

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20 Jul 2009, 03:39
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)%
Intern
Joined: 29 Jun 2008
Posts: 15
Re: Probability and Time Distance Question  [#permalink]

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20 Jul 2009, 19:17
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 ....

Regards,
Aban
Senior Manager
Joined: 23 Jun 2009
Posts: 353
Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago
Re: Probability and Time Distance Question  [#permalink]

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21 Jul 2009, 00:11
Look at this file. This problem is a decision tree problem.

--== Message from GMAT Club Team ==--

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If you would like to discuss this question please re-post it in the respective forum. Thank you!

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Attachments

dectree.JPG [ 13.3 KiB | Viewed 1199 times ]

Re: Probability and Time Distance Question &nbs [#permalink] 21 Jul 2009, 00:11
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