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rhinoceros horns

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by thephoenix » Mon May 03, 2010 9:58 pm
Because of the lucrative but illegal trade in rhinoceros horns, a certain rhinoceros species has been hunted nearly to extinction. Therefore an effective way to ensure the survival of that species would be to periodically trim off the horns of all rhinoceroses, thereby eliminating the motivation for poaching.
Which one of the following is an assumption required by the argument?
(A) Most poachers who are discouraged from hunting rhinoceroses are not likely to hunt other animals for their horns.
(B) At lease some rhinoceroses whose horns are periodically trimmed off will be able to attract mates.
(C) Poachers hunt at lease some immature rhinoceroses whose horns have not yet started to develop.
(D) The demand for rhinoceros horns will remain constant even if the supply decreases after the periodical trimming-off of the rhinoceros horns has begun.
(E) Rhinoceroses whose horns have been trimmed off are unable to defend themselves against predators.

[spoiler]none of the answers seems right to me;pls help[/spoiler]
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by magizhan » Mon May 03, 2010 10:19 pm
IMO B

if B is not assumed then survival of rhinoceros species wouldn't be possible.
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by orel » Mon May 03, 2010 11:58 pm
It should be D

The conclusion states "...periodically trimming off the horns will eliminate the motivation for poaching".
There is an assumption that the demand for these horns will stay constant. That is the reason of a periodical-trimming-off offer.

Please correct me if I am wrong
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by Testluv » Tue May 04, 2010 12:18 am
magizhan wrote:IMO B

if B is not assumed then survival of rhinoceros species wouldn't be possible.
great reasoning!

____________

The question asks for an assumption required by the argument. Because it is a necessary assumption question, we can use the Kaplan denial test.

Choice B reads:
B) At least some rhinoceroses whose horns are periodically trimmed off will be able to attract mates.
whose denial is:

"none of the rhinoceroses whose horns are periodically trimmed off will be able to attract mates"

in which case, rather than ensuring survival, trimming off their horns would ensure the extinction of the species.

Because the denial of choice B kills the argument, choice B itself is an assumption required by the argument.
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by sumanr84 » Tue May 04, 2010 1:07 am
Testluv wrote:
magizhan wrote:IMO B

Choice B reads:
B) At least some rhinoceroses whose horns are periodically trimmed off will be able to attract mates.
whose denial is:

"none of the rhinoceroses whose horns are periodically trimmed off will be able to attract mates"

in which case, rather than ensuring survival, trimming off their horns would ensure the extinction of the species.

Because the denial of choice B kills the argument, choice B itself is an assumption required by the argument.
I never used so much of denial test in digging Assumption question but last few question posted by thephoenix really twisted me a lot. I enjoyed the explanation given above by Testluv and will try to follow them in assumption qs hereon.
Thanks to Testluv & thephoenix
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by gmatmachoman » Tue May 04, 2010 7:22 am
sumanr84 wrote:
Testluv wrote:
magizhan wrote:IMO B

Choice B reads:
B) At least some rhinoceroses whose horns are periodically trimmed off will be able to attract mates.
whose denial is:

"none of the rhinoceroses whose horns are periodically trimmed off will be able to attract mates"

in which case, rather than ensuring survival, trimming off their horns would ensure the extinction of the species.

Because the denial of choice B kills the argument, choice B itself is an assumption required by the argument.
I never used so much of denial test in digging Assumption question but last few question posted by thephoenix really twisted me a lot. I enjoyed the explanation given above by Testluv and will try to follow them in assumption qs hereon.
Thanks to Testluv & thephoenix
@suman/@phenix..

If we keep a "counter" of how many has favoured TestLuv, it would be Infinity-1...becox that "1" belongs to TestLuv himself..

Dada is impeccable when comes to reasoning!!
Actually he has been a great motivator for me and many more!!
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by ru2008 » Tue May 04, 2010 7:54 am
Whats wrong w D?
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by Testluv » Tue May 04, 2010 9:53 pm
ru2008 wrote:Whats wrong w D?
I can see why choice D is tempting!

Choice D is outside the scope. As far as chances of the rhinos' survival are concerned, changes in demand should be irrelevant if the supply of horns is zero. If the poachers want more and more horns, they won't get them by killing rhinos whose horns have already been removed.
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by viidyasagar » Thu May 13, 2010 5:01 pm
Because of the lucrative but illegal trade in rhinoceros horns, a certain rhinoceros species has been hunted nearly to extinction. Therefore an effective way to ensure the survival of that species would be to periodically trim off the horns of all rhinoceroses, thereby eliminating the motivation for poaching
I don't get this!!!

It seems to me that we have chosen our own conclusion to force-fit B....."B" has got nothing to do with poaching and the heart of this argument is "cracking ways to eliminate poaching"

I have heard that nothing on the GMAT is superfluous....the explanation here is insane, retarded!!!....the only way B is right is if consider only this..... "an effective way to ensure the survival of that species would be to periodically trim off the horns of all rhinoceroses"

Testluv, i have tremendous respect for you sirji, isn't this question out of scope???

My prediction of the answer: Only sharp horns motivate poachers............OR.........Poachers hunting a dangerous animal like a rhino hunt from a safe distance and sharpness of horns is clearly visible from there

If i personalise this argument, there is no chance in hell/ heaven that i will go for B....please help
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by Testluv » Thu May 13, 2010 9:21 pm
Wow!

Okay. The two assumptions you mention are also necessary assumptions (although for your first, instead of "too sharp" we should plug in "horns that are not periodically trimmed off"), and they are great predictions.

Unfortunately, neither of them showed up among the answer choices.

In (necessary) assumption questions, when we don't find an answer choice that matches our (great) prediction(s), we should immediately resort to the denial test.

We can use the denial test to prove that choice B is correct, and the basis of choice B's correctness is that it is the only answer choice that satisfies the demands of the question stem. The question stem ask for an assumption required by the argument. In other words, the right answer is an idea that is necessary to the argument's reasoning; it is an idea without which the argument would fail to logically "stand up".

As I explained in my post above, if we negate choice B's truth, then the argument is not able to logically stand: if rhinos whose horns are trimmed are unable to reproduce, then their survival is definitely not ensured--in fact, their extinction is ensured. Following the author's plan of trimming the rhinos' horns would actually lead to an outcome opposite of the one intended by the author.

So, when B is untrue, the argument shatters. Thus, B must be true in order for the argument to stand: it is an idea--an assumption--required by the argument.

__________

I think the reason why one might find choice B hard to swallow as correct has to do with the following.

Choice B is different from most correct answers to assumption questions in that it does not bridge a gap between the evidence and the conclusion. Instead, choice B points to a consideration the author may have overlooked in the first place before he even began proceeding from the evidence to conclusion. I call these assumptions "anterior" rather than "central". Anterior assumptions are difficult to predict because they don't necessarily reflect flawed reasoning; quite often the assumption is fair to make. (Instead, we would walk into the answer choices with the kinds of predictions that you had generated.) Because we would rarely ever predict such an assumption, using denial test is really the only way of spotting one. Sorry if that's kind of abstract but here's another example of one: https://www.beatthegmat.com/powerscore-q ... 54353.html
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by viidyasagar » Thu May 13, 2010 9:42 pm
Learnt something new!!!! Anterior assumptions, never to pre-phrase on assumptions. Infact, go, straighaway, into denial mode!!!

Testluv, I bow to thee...how do i become like you???

This Q is GMATesque for sure, isn't it?
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by Testluv » Thu May 13, 2010 9:52 pm
viidyasagar wrote:Learnt something new!!!! Anterior assumptions, never to pre-phrase on assumptions. Infact, go, straighaway, into denial mode!!!

Testluv, I bow to thee...how do i become like you???

This Q is GMATesque for sure, isn't it?
Hi,

to be clear, I am definitely not saying "never prephrase" in assumption questions. I'm saying DO make a prediction (and, again, your predictions were great). BUT, if you don't find a match to your prediction, then go into denial test mode.

This is a fine "GMATesque" question!
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