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The arguments conclusion is that if the temperature NEVER gets above 95 degrees then the number of rings is an accurace prediction of the tree's age.

(E) says that:
The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is not predictable

No one cares about what happens when the temp gets over 95 degrees, the arguments scope is only below 95 degrees.

A is right because if there is another factor that the author did not consider in predicting the tree's age -- PRECIPITATION -- then the argument falls apart and this has to be our assumption.

Its not a great question IMO, but I stick to my guns with A.

Re: CR: Explain this [#permalink]
06 Jan 2007, 11:57

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

A and E both seem correct but still a bit confusing........

A. If more percipatation => more rings. then age of the tree according to the rings is misleading because the tree has one ring/year. therefore, percipatation shouldnot cause to have more rings.

E. if we know the number of rings lost due to the tempreture that exceeds 95 degrees fahrenheight, then still we can identify the age of the tree and the lost rings have no effect in finding the age of the tree. so if temp>95 and we donot know the lost rings, it is not possible to find the age of the tree. otherwise, yes. the passage says that if there were no temp >95, the no of rings are reliable measure of tree's age. even if there were temp>95 and we donot know the lost rings because of temp>95, then the no of rings are not reasonable measure of the tree's age.

If the number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is predictable, then tree's age can be determined by counting the number of internal rings.

Re: CR: Explain this [#permalink]
07 Jan 2007, 08:34

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

The key concept in the conclusion is reliable measure given the temperature doesnÂ´t exceed 95 F. Which is the only answer choice that addresses it? A. E is the 2nd best, although it is out of scope bc it deals w/ an scenario not contemplated in the conclusion (T > 95 F).

Re: CR: Explain this [#permalink]
07 Jan 2007, 08:35

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

The key concept in the conclusion is reliable measure given the temperature doesnÂ´t exceed 95 F. Which is the only answer choice that addresses it? A. E is the 2nd best, although it is out of scope bc it deals w/ an scenario not contemplated in the conclusion (T > 95 F).

(E) CORRECT. The conclusion is that the rings will be a reliable measure only if the temperature never exceeds 95 degrees. This is true only if there is no way to predict how many rings would be lost when the temperature does exceed 95 degrees. (If it were possible to predict this, one might be able to assess the age of a tree using its rings even if the temperature had exceeded 95 degrees.)

however i also think this question is strange... i also can live with answer choice C since the author says "never exceeds 95 degrees", i.e. there is an assumption that an exceeding at one day is enough...