There is at least one viper and at least one cobra in Pandora's box. How many cobras are there?
(1) From any two snakes from Pandora's box at least one is a viper.
(2) The total number of snakes Pandora's box is 99.
Tough DS
This topic has expert replies
-
- Master | Next Rank: 500 Posts
- Posts: 391
- Joined: Sat Mar 02, 2013 5:13 am
- Thanked: 50 times
- Followed by:4 members
- theCodeToGMAT
- Legendary Member
- Posts: 1556
- Joined: Tue Aug 14, 2012 11:18 pm
- Thanked: 448 times
- Followed by:34 members
- GMAT Score:650
V >= 1
C >= 1
To find: C?
Statement 1:
This means that there is only ONE other SNAKE except VIPER.. and its clear in question that there is atleast one COBRA..So, COBRA = 1
SUFFICIENT
Statement 2:
V+C = 99
INSUFFICIENT
is it {A}?
C >= 1
To find: C?
Statement 1:
This means that there is only ONE other SNAKE except VIPER.. and its clear in question that there is atleast one COBRA..So, COBRA = 1
SUFFICIENT
Statement 2:
V+C = 99
INSUFFICIENT
is it {A}?
Last edited by theCodeToGMAT on Thu Oct 17, 2013 10:10 pm, edited 1 time in total.
R A H U L
-
- Master | Next Rank: 500 Posts
- Posts: 468
- Joined: Mon Jul 25, 2011 10:20 pm
- Thanked: 29 times
- Followed by:4 members
- theCodeToGMAT
- Legendary Member
- Posts: 1556
- Joined: Tue Aug 14, 2012 11:18 pm
- Thanked: 448 times
- Followed by:34 members
- GMAT Score:650
Vipul what if there were say total 10 snakes andvipulgoyal wrote:Probablity of Viper cant be 1 because in box there is at least 1 viper and one C,Is OA A ???
DRAW 1: VV
DRAW 2: VC
DRAW 3: VC
DRAW 4: VV
DRAW 5: VC
Yes, I agree that Answer must be {A} but not because of the reason you sighted.
The condition Stated in Statement 1 means that there is only ONE OTHER SNAKE..and that's COBRA
R A H U L
-
- Master | Next Rank: 500 Posts
- Posts: 468
- Joined: Mon Jul 25, 2011 10:20 pm
- Thanked: 29 times
- Followed by:4 members
I didnt gave ne explaination before,by saying so I contradicted the ans, you initially stated as "E before
- theCodeToGMAT
- Legendary Member
- Posts: 1556
- Joined: Tue Aug 14, 2012 11:18 pm
- Thanked: 448 times
- Followed by:34 members
- GMAT Score:650
I commented on your comment that "Probability can't be 1".. it can definitely be.vipulgoyal wrote:I didnt gave ne explaination before, I think you initially stated E as ans ??
Yes, initially I had misunderstood the question, assuming that it meant withdrawal. That's why I considered the Probability; but the question is, infact, much direct.
R A H U L
-
- Master | Next Rank: 500 Posts
- Posts: 391
- Joined: Sat Mar 02, 2013 5:13 am
- Thanked: 50 times
- Followed by:4 members
GMAT/MBA Expert
- [email protected]
- Elite Legendary Member
- Posts: 10392
- Joined: Sun Jun 23, 2013 6:38 pm
- Location: Palo Alto, CA
- Thanked: 2867 times
- Followed by:511 members
- GMAT Score:800
Hi All,
It seems as though everyone has gotten the correct answer, but since the explanations that have been offered are a bit "lean", here is why the answer is A:
We're told there's at least 1 viper and at least 1 cobra in the box. The question asks for the number of cobras.
Fact 1: If you pick any 2 snakes, you'll get AT LEAST 1 viper.
So, if you were grabbing snakes one at a time, according to Fact 1, you COULD GET:
VC
CV
VV
You COULD NOT GET:
CC
The only way to guarantee that you won't get CC is if there was ONLY ONE COBRA.
Fact 1 is SUFFICIENT
Fact 2: Total number of snakes = 99
There's not enough info to determine how many of the 99 are cobras.
Fact 2 is INSUFFICIENT.
GMAT assassins aren't born, they're made,
Rich
It seems as though everyone has gotten the correct answer, but since the explanations that have been offered are a bit "lean", here is why the answer is A:
We're told there's at least 1 viper and at least 1 cobra in the box. The question asks for the number of cobras.
Fact 1: If you pick any 2 snakes, you'll get AT LEAST 1 viper.
So, if you were grabbing snakes one at a time, according to Fact 1, you COULD GET:
VC
CV
VV
You COULD NOT GET:
CC
The only way to guarantee that you won't get CC is if there was ONLY ONE COBRA.
Fact 1 is SUFFICIENT
Fact 2: Total number of snakes = 99
There's not enough info to determine how many of the 99 are cobras.
Fact 2 is INSUFFICIENT.
GMAT assassins aren't born, they're made,
Rich
-
- Master | Next Rank: 500 Posts
- Posts: 468
- Joined: Mon Jul 25, 2011 10:20 pm
- Thanked: 29 times
- Followed by:4 members
Hi Rahul, I still agree that P cant be 1, suppose VVVC. in two picks 2 viper 3/4*2/3 = 1/2, in two picks one V and 1 C = 3/4 * 1/3 * 2 = 1/2 , you may take ne numbers of Vipers untill we have one C we cant have P = 1,
- theCodeToGMAT
- Legendary Member
- Posts: 1556
- Joined: Tue Aug 14, 2012 11:18 pm
- Thanked: 448 times
- Followed by:34 members
- GMAT Score:650
Hello Vipul, I guess we are trying to refer probability in different context ..vipulgoyal wrote:Hi Rahul, I still agree that P cant be 1, suppose VVVC. in two picks 2 viper 3/4*2/3 = 1/2, in two picks one V and 1 C = 3/4 * 1/3 * 2 = 1/2 , you may take ne numbers of Vipers untill we have one C we cant have P = 1,
Yes the context which you are referring.. we will never have probability as "1".
R A H U L
- sanju09
- GMAT Instructor
- Posts: 3650
- Joined: Wed Jan 21, 2009 4:27 am
- Location: India
- Thanked: 267 times
- Followed by:80 members
- GMAT Score:760
(1) This statement guarantees that there's only one cobra in the box. Had it not been the case, then we could not have witnessed :rakeshd347 wrote:There is at least one viper and at least one cobra in Pandora's box. How many cobras are there?
(1) From any two snakes from Pandora's box at least one is a viper.
(2) The total number of snakes Pandora's box is 99.
: happening. This alone is sufficient.From any two snakes from Pandora's box at least one is a viper
(2) From the total of the two positive integers, in which one has to be at least 1, we cannot take out the exact value of one of the two positive integers. This alone is hence [spoiler]insufficient.
Hence (A) is the correct answer.[/spoiler]
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001
www.manyagroup.com
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001
www.manyagroup.com
- sanju09
- GMAT Instructor
- Posts: 3650
- Joined: Wed Jan 21, 2009 4:27 am
- Location: India
- Thanked: 267 times
- Followed by:80 members
- GMAT Score:760
What PROBABILITY serves here?vipulgoyal wrote:Hi Rahul, I still agree that P cant be 1, suppose VVVC. in two picks 2 viper 3/4*2/3 = 1/2, in two picks one V and 1 C = 3/4 * 1/3 * 2 = 1/2 , you may take ne numbers of Vipers untill we have one C we cant have P = 1,
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001
www.manyagroup.com
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001
www.manyagroup.com
- theCodeToGMAT
- Legendary Member
- Posts: 1556
- Joined: Tue Aug 14, 2012 11:18 pm
- Thanked: 448 times
- Followed by:34 members
- GMAT Score:650
sanju09 wrote:What PROBABILITY serves here?[/quotevipulgoyal wrote:Hi Rahul, I still agree that P cant be 1, suppose VVVC. in two picks 2 viper 3/4*2/3 = 1/2, in two picks one V and 1 C = 3/4 * 1/3 * 2 = 1/2 , you may take ne numbers of Vipers untill we have one C we cant have P = 1,
Nothing Sanjeev .. Was just trying to look question from different prospective.
Thanks!
R A H U L
GMAT/MBA Expert
- Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
Given: There is at least one viper and at least one cobra in Pandora's box.rakeshd347 wrote:There is at least one viper and at least one cobra in Pandora's box. How many cobras are there?
(1) From any two snakes from Pandora's box at least one is a viper.
(2) The total number of snakes Pandora's box is 99.
Target question: How many cobras are there?
Statement 1: From any two snakes from Pandora's box at least one is a viper.
This tells us that there CANNOT be more than one cobra in the box.
For example, if there were TWO cobras and the box, then it's possible to have two snakes (both cobras) such that neither is a viper, which would break the condition that at least one snake must be a viper.
Since we are told there is at least one cobra, and since we have now concluded that there CANNOT be more than one cobra in the box, the answer to the target question is there is exactly 1 cobra in the box
Since we can answer the target question with certainty, statement 1 is SUFFICIENT
Statement 2: The total number of snakes in Pandora's box is 99
There are many scenarios that satisfy statement 2. Here are two:
Case a: There are 10 cobras and 89 vipers. In this case, the answer to the target question is there are 10 cobras in the box
Case b: There are 11 cobras and 88 vipers. In this case, the answer to the target question is there are 11 cobras in the box
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
Cheers,
Brent