BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Probability and combinations

This topic has expert replies
Post new topic Locked
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 222
Joined: Mon Oct 13, 2008 4:04 pm
Thanked: 3 times
Followed by:2 members

Probability and combinations

by venmic » Sat Aug 07, 2010 8:20 am
Denise is trying to open a safe whose combination she does not know If the safe has 4000 possible combinations and she can try 75 different possibilities what is the probability that she does not pick the one correct combination

1
159/160
157/160
3/160
0

Do not know answer
This is a Kaplan question
Top
Source: — Sentence Correction |
User avatar
Legendary Member
Posts: 1893
Joined: Sun May 30, 2010 11:48 pm
Thanked: 215 times
Followed by:7 members

by kvcpk » Sat Aug 07, 2010 8:28 am
venmic wrote:Denise is trying to open a safe whose combination she does not know If the safe has 4000 possible combinations and she can try 75 different possibilities what is the probability that she does not pick the one correct combination

1
159/160
157/160
3/160
0

Do not know answer
This is a Kaplan question
Buddy.. Can you post this in the right forum? - Problem Solving.
Top
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 am
Thanked: 137 times
Followed by:5 members

by thephoenix » Sat Aug 07, 2010 8:37 am
moderators please transfer the question in right forum

ans should be c

probability of getting a correct combination is 75/4000=3/160
P of not getting any correct combination is 1-3/160=157/160
Many of the great achievements of the world were accomplished by tired and discouraged men who kept on working
Top
Master | Next Rank: 500 Posts
Posts: 222
Joined: Mon Oct 13, 2008 4:04 pm
Thanked: 3 times
Followed by:2 members

by venmic » Sat Aug 07, 2010 9:49 am
sorry about that

but the last post came as

probability of getting a correct combination is 75/4000=3/160

can you plaease explain the concept of a 75/4000
I mean the logic behind it

Thanks for ur help
Top
User avatar
Legendary Member
Posts: 1893
Joined: Sun May 30, 2010 11:48 pm
Thanked: 215 times
Followed by:7 members

by kvcpk » Sat Aug 07, 2010 10:23 am
venmic wrote:sorry about that

but the last post came as

probability of getting a correct combination is 75/4000=3/160

can you plaease explain the concept of a 75/4000
I mean the logic behind it

Thanks for ur help
Probability of good outcomes = (Number of good outcomes)/ Total Outcomes
Number of good outcomes here are 75
Total number of outcomes = 4000
Hence probability = 75/4000

Now we require bad outcomes probability. hence subtract the result from 1
1= 75/4000 = 157/160

Hope this helps!!
Top
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 am
Thanked: 137 times
Followed by:5 members

by thephoenix » Sat Aug 07, 2010 10:29 am
venmic wrote:sorry about that

but the last post came as

probability of getting a correct combination is 75/4000=3/160

can you plaease explain the concept of a 75/4000
I mean the logic behind it

Thanks for ur help
there is only one combination for opening the safe out of 4000
now Denise is trying 75 combination
now if the combination exists in these 75 trials then denise can do it in 75C1 ways=75
he can select one combination out of 4000 combination in 4000 ways
so probability of getting a correct combination is 75/4000

hth
Many of the great achievements of the world were accomplished by tired and discouraged men who kept on working
Top
Master | Next Rank: 500 Posts
Posts: 222
Joined: Mon Oct 13, 2008 4:04 pm
Thanked: 3 times
Followed by:2 members

by venmic » Sat Aug 07, 2010 1:08 pm
Thankyou Sir
Top
User avatar
Senior | Next Rank: 100 Posts
Posts: 82
Joined: Thu May 27, 2010 12:23 pm
Location: Newyork
Thanked: 2 times
Followed by:3 members

by selfmade » Sun Aug 08, 2010 6:54 am
one more vote for 157/160. The explaination provided by thephoneix is really good.
----------
Aiming for 780
Top
Post new topic Locked
• Page 1 of 1