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The popular notion that a tree's age can be determined by [#permalink]
 07 Dec 2006, 20:27
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The popular notion that a tree's age can be determined by counting the number of internal rings in its trunk is generally true. However, to help regulate the internal temperature of the tree, the outermost layers of wood of the Brazilian ash often peel away when the temperature exceeds 95 degrees Fahrenheit, leaving the tree with fewer rings than it would otherwise have. So if the temperature in the Brazilian ash's environment never exceeded 95 degrees Fahrenheit, its rings would be a reliable measure of the tree's age.
Which of the following is an assumption on which the argument above depends?
(A) The growth of new rings in a tree is not a function of levels of precipitation.
(B) Only the Brazilian ash loses rings because of excessive heat.
(C) Only one day of temperatures above 95 degrees Fahrenheit is needed to cause the Brazilian ash to lose a ring.
(D) The internal rings of all trees are of uniform thickness.
(E) The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is not predictable
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Quote: The popular notion that a tree's age can be determined by counting the number of internal rings in its trunk is generally true. However, to help regulate the internal temperature of the tree, the outermost layers of wood of the Brazilian ash often peel away when the temperature exceeds 95 degrees Fahrenheit, leaving the tree with fewer rings than it would otherwise have. So if the temperature in the Brazilian ash's environment never exceeded 95 degrees Fahrenheit, its rings would be a reliable measure of the tree's age.
Which of the following is an assumption on which the argument above depends?
(A) The growth of new rings in a tree is not a function of levels of precipitation.
(B) Only the Brazilian ash loses rings because of excessive heat.
(C) Only one day of temperatures above 95 degrees Fahrenheit is needed to cause the Brazilian ash to lose a ring.
(D) The internal rings of all trees are of uniform thickness.
(E) The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is not predictable
No mention is made of ring thickness. D is out.
We are asked "So if the temperature in the Brazilian ash's environment never exceeded 95 degrees Fahrenheit, its rings would be a reliable measure of the tree's age?" C and E discuss the environment temperature exceeding 95 degrees. C and E are out.
If B had said something like "The Brazilian Ash is representative of all trees" I'd go with B. B, as it's stated, weakens the argument. B is out.
I'd have to go with A. .... me thinks
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AGree with A.
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Re: CR: Explain this [#permalink]
07 Dec 2006, 20:59
Swagatalakshmi wrote: The popular notion that a tree's age can be determined by counting the number of internal rings in its trunk is generally true. However, to help regulate the internal temperature of the tree, the outermost layers of wood of the Brazilian ash often peel away when the temperature exceeds 95 degrees Fahrenheit, leaving the tree with fewer rings than it would otherwise have. So if the temperature in the Brazilian ash's environment never exceeded 95 degrees Fahrenheit, its rings would be a reliable measure of the tree's age.
Which of the following is an assumption on which the argument above depends?
(A) The growth of new rings in a tree is not a function of levels of precipitation.
(B) Only the Brazilian ash loses rings because of excessive heat.
(C) Only one day of temperatures above 95 degrees Fahrenheit is needed to cause the Brazilian ash to lose a ring.
(D) The internal rings of all trees are of uniform thickness.
(E) The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is not predictable
I am somewhere among A, C and E
In E: Probably it does not matter whether we know the the number of rings lost when temperature exceeds 95 degrees. If we knew, say, teh tree loses 1 ring when the temp exceeds 95 degrees. we do not know how many days was the temperature over 95 degrees during the tree's lifetime (since we do not know tree's ag eto begin with)
A: I don't think we are really concerned about how the rings grow. The concern is how the rings can decrease
By POE, C seems to be the choice though it is a little strong because of the usage of only.
The information in the paragraph says: So if the temperature in the Brazilian ash's environment never exceeded 95 degrees Fahrenheit, its rings would be a reliable measure of the tree's age. Usage of never seems to indicate that if the temperature is over 95 degrees on even 1 day, then the tree should at least lose 1 ring.
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I say E
The passage says that <95 degree, the rings would be a reliable measure. It must have assumed E
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E makes the most sense to me
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I like A.
The passage says that the number of rings is affected by temperature and that if the tempearatures do not reach the 95 deg, then the rings are an accurate measure of the life of the tree.
This will be true only if there are no other factors that affect ring growth/ring shed.
If A (The growth of new rings in a tree is not a function of levels of precipitation)is false, then this argument will not hold water. So A has to be true.
So A must be the assumption.
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Going for A ...
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Re: CR: Explain this [#permalink]
08 Dec 2006, 02:20
Swagatalakshmi wrote: The popular notion that a tree's age can be determined by counting the number of internal rings in its trunk is generally true. However, to help regulate the internal temperature of the tree, the outermost layers of wood of the Brazilian ash often peel away when the temperature exceeds 95 degrees Fahrenheit, leaving the tree with fewer rings than it would otherwise have. So if the temperature in the Brazilian ash's environment never exceeded 95 degrees Fahrenheit, its rings would be a reliable measure of the tree's age.
Which of the following is an assumption on which the argument above depends?
(A) The growth of new rings in a tree is not a function of levels of precipitation.
If the precipitation is causing new rings, and taking away them then there wont be any change in the number of rings that are supposed to be there. There will be net reduction in the number, only when the precipitation does not increase the number of rings, but takes away some of them.
(B) Only the Brazilian ash loses rings because of excessive heat.
(C) Only one day of temperatures above 95 degrees Fahrenheit is needed to cause the Brazilian ash to lose a ring.
(D) The internal rings of all trees are of uniform thickness.
(E) The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is not predictable
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Director
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I say E...
A is out of scope.....
Argument says that it is impossible to determine the age of the Brazilian ash if the temperature exceeds 95 F, because the tree peels away some layers of wood... And the number of layers of wood is an indication of age....
Thus it is assumed that there is no way to calculate the number of layers the tree will loose in high temperatures....
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Another E for me. The author states that the Brazilian ash age can be reliably measured when temperature never went above 95, implying that it cannot be reliably measured otherwise.
Editing:
I am now going towards A. The conclusion says: So if the temperature in the Brazilian ash's environment never exceeded 95 degrees Fahrenheit, its rings would be a reliable measure of the tree's age.
The conclusion is all about how reliable it is to estimate age when temp is below 95. So A comes up as an assumption.
I am learning (slowly) not to look into what the author is trying to imply, or what I think the author is trying to imply, but take the sentence at face value.
Last edited by mbagal1 on 08 Dec 2006, 11:49, edited 2 times in total.
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Quote: I like A.
The passage says that the number of rings is affected by temperature and that if the tempearatures do not reach the 95 deg, then the rings are an accurate measure of the life of the tree.
This will be true only if there are no other factors that affect ring growth/ring shed.
If A (The growth of new rings in a tree is not a function of levels of precipitation)is false, then this argument will not hold water. So A has to be true.
So A must be the assumption.
exactly my thoughts, ncprasad. A for me too.
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I'm going for E.
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I'm going for E.
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Another E
OA Please
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hmmm .... 6/6 split between A and E ... I was with E but the OA is A.
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Swagatalakshmi,
Can we have the OR (official reasoning)?
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I don't have OE.
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Re: CR: Explain this [#permalink]
10 Dec 2006, 22:50
Swagatalakshmi wrote: The popular notion that a tree's age can be determined by counting the number of internal rings in its trunk is generally true. However, to help regulate the internal temperature of the tree, the outermost layers of wood of the Brazilian ash often peel away when the temperature exceeds 95 degrees Fahrenheit, leaving the tree with fewer rings than it would otherwise have. So if the temperature in the Brazilian ash's environment never exceeded 95 degrees Fahrenheit, its rings would be a reliable measure of the tree's age.
Argument1: TreeAge<=NumberOfRings
Argument2: If Temp>95, TreeAge<=NumberOfRings
Conclusion: If Temp<=95, TreeAge=NumberOfRings
Assumption needed would be there is no other factors that will cause less number of rings other than temp>95.
Compare this to the following options, A is remotely possible because it talks about precipitation not being a factor that determines number of rings. B through E are irrelevent. A isn't the best answer, in my opinion, but is the only possible one in the choices given.
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I'm going with F, none of the above.
I have thought about this question for about a half hour now, and F is my final answer.
The conclusion states that the tree's age can be reliably determined by the rings. An approiate assumption would be:
The "Brazilian ash" grows at a rate that is consistent with other trees, whose age can be determined by the number of rings in it's trunk".
Bringing precipitation into the equation is out of scope.
IMO, this is a garbage question.
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