Go Back   TestMagic Forums > Test preparation > GRE > GRE Math
Register Forum Rules FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old 2005 June 12th, 04:01 PM   #21 (permalink)
Within my grasp!
 
Join Date: Jun 2005
Posts: 388
Dkumar just joined TestMagic.
Re: one probability question

Hi Brinda!
I get a different answer for your question.

On any day in April in a certain city, the probability of rain is 50%. What is the probability of that it rains exactly 5 days during a 7 day period in April?

Acc to my calculation,

Probability that it will rain in a any day is 1/2
Prabability that it will not rain is (1-1/2) = 1/2
Probability that it will rain exactly 5 days and will not rain the other two days = 1/2 *1/2*1/2*1/2*1/2*1/2*1/2 = 1/128

Please let me know the correct answer.
Thanks.
_ _ _ _ SIG _ _ _ _
Dinesh
Dkumar is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Old 2005 June 12th, 04:41 PM   #22 (permalink)
TestMagic Guru
 
manasi4gre's Avatar
 
Join Date: Nov 2004
Location: INDIA
Posts: 1,810
manasi4gre is a TestMagic guru. Show your respect!manasi4gre is a TestMagic guru. Show your respect!
Re: one probability question

Quote:
Originally Posted by Dkumar
The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to be tossed three times, what is the probability that on at least one of the tosses the coin will turn up heads?
The answer is 3/8.
How did u get this answer?
_ _ _ _ SIG _ _ _ _

"Fear less,hope more; whine less,breathe more;
Talk less,work more; hate less,love more;
Then all the good things are yours ."

---Proverb---
manasi4gre is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Old 2005 June 12th, 05:35 PM   #23 (permalink)
ish
Dumbledore's Army
 
ish's Avatar
 
Join Date: Jan 2005
Posts: 2,334
ish is a member of the TestMagic inner circle.ish is a member of the TestMagic inner circle.ish is a member of the TestMagic inner circle.ish is a member of the TestMagic inner circle.
Re: one probability question

Quote:
Originally Posted by Dkumar
Hi Brinda!
I get a different answer for your question.

On any day in April in a certain city, the probability of rain is 50%. What is the probability of that it rains exactly 5 days during a 7 day period in April?

Acc to my calculation,

Probability that it will rain in a any day is 1/2
Prabability that it will not rain is (1-1/2) = 1/2
Probability that it will rain exactly 5 days and will not rain the other two days = 1/2 *1/2*1/2*1/2*1/2*1/2*1/2 = 1/128

Please let me know the correct answer.
Thanks.
Kumar,you have to use the binomial method here.
nCr(p)^r(q)^n-r
so here its
7C2(50/100)5(50/100)2
which is
21(1/2)^7
_ _ _ _ SIG _ _ _ _
If you can't change your mind, are you sure you have one?

Be weird whenever you have the chance

Don't lurk! Please participate

OF COURSE I DON'T LOOK BUSY...I DID IT RIGHT THE FIRST TIME.
ish is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Old 2005 June 12th, 06:22 PM   #24 (permalink)
TestMagic Guru
 
manasi4gre's Avatar
 
Join Date: Nov 2004
Location: INDIA
Posts: 1,810
manasi4gre is a TestMagic guru. Show your respect!manasi4gre is a TestMagic guru. Show your respect!
Re: one probability question

ish, why cant we use the other approach?
_ _ _ _ SIG _ _ _ _

"Fear less,hope more; whine less,breathe more;
Talk less,work more; hate less,love more;
Then all the good things are yours ."

---Proverb---
manasi4gre is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Old 2005 June 12th, 06:25 PM   #25 (permalink)
ish
Dumbledore's Army
 
ish's Avatar
 
Join Date: Jan 2005
Posts: 2,334
ish is a member of the TestMagic inner circle.ish is a member of the TestMagic inner circle.ish is a member of the TestMagic inner circle.ish is a member of the TestMagic inner circle.
Re: one probability question

because you have to account for the number of ways you can choose 5 out of 7, and then compute their respective probabilities. its also a question of choice, isnt it?
_ _ _ _ SIG _ _ _ _
If you can't change your mind, are you sure you have one?

Be weird whenever you have the chance

Don't lurk! Please participate

OF COURSE I DON'T LOOK BUSY...I DID IT RIGHT THE FIRST TIME.
ish is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Old 2005 June 12th, 06:28 PM   #26 (permalink)
TestMagic Guru
 
manasi4gre's Avatar
 
Join Date: Nov 2004
Location: INDIA
Posts: 1,810
manasi4gre is a TestMagic guru. Show your respect!manasi4gre is a TestMagic guru. Show your respect!
Re: one probability question

yes I know that.. was actually wondering about the other approach..anyway, the solution is clear now.
_ _ _ _ SIG _ _ _ _

"Fear less,hope more; whine less,breathe more;
Talk less,work more; hate less,love more;
Then all the good things are yours ."

---Proverb---
manasi4gre is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Old 2005 June 12th, 10:54 PM   #27 (permalink)
Within my grasp!
 
Join Date: Jun 2005
Posts: 388
Dkumar just joined TestMagic.
Re: one probability question

Yeah you are right. I have to work more in this area.
Thanks a lot ish. Keep posting more problems brinda.
_ _ _ _ SIG _ _ _ _
Dinesh
Dkumar is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Old 2005 June 17th, 06:53 AM   #28 (permalink)
Within my grasp!
 
brindha_arun's Avatar
 
Join Date: Mar 2005
Posts: 130
brindha_arun just joined TestMagic.
thanks dinesh for thy encouragement. i will try to post as many problems as i can



Quote:
Originally Posted by Dkumar
Yeah you are right. I have to work more in this area.
Thanks a lot ish. Keep posting more problems brinda.
brindha_arun is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Old 2005 June 17th, 12:44 PM   #29 (permalink)
I JUST got here.
 
Join Date: Jun 2005
Posts: 19
vit11 just joined TestMagic.
______

Last edited by vit11 : 2005 June 17th at 12:48 PM. Reason: didn't see that a solution was already posted
vit11 is offline  
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!Google Bookmark this Post!Reddit!
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

What you can do
You cannot post new threads
You cannot post replies
You cannot post attachments
You cannot edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


All times are GMT. The time now is 11:41 PM.

Contact TestMagic   TestMagic Forums      Archive   Privacy Statement

TestMagic Locations   Legal   Privacy


SEO by vBSEO 3.2.0
Copyright © 2009 TestMagic
Ad Management by RedTyger

Scroll Up