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The popular notion that a tree's age can be determined by [#permalink]
13 Oct 2009, 06:54
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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 only if the temperature in the Brazilian ash's environment never exceeds 95 degrees Fahrenheit will its rings 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
Round 1 A - This can be right B - This is being clearly stated in the argument and is therefore not an assumption C - This can be right D - This is not at al relevant to the premise or the conclusion E - This has also been stated in the argument and should therefore not be an assumption
Round 2 We are left with A and C. "A" - "A" is more appropriate because it affects the conclusion directly, if this is the assumption only then conclusion can be true. "C" - for how long the temprature should stay at 95 for the ring to shed is no where being mentioned either in the premise or in conclusion..it therefore seems un-related.
- Its all about correctness first and then the timing.
The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is not predictable
As we cannot predict how many rings were lost because of the temperature fluctuations,we cannot predict the age of the tree. - I would go for this choice.
A. The growth of new rings in a tree is not a function of levels of precipitation. - Irrelevant B. Only the Brazilian ash loses rings because of excessive heat. - Out of Scope C. Only one day of temperatures above 95 degrees Fahrenheit is needed to cause the Brazilian ash to lose a ring. - Out of Scope D. The internal rings of all trees are of uniform thickness. - Irrelevant
Keep trying no matter how hard it seems, it will get easier.
Try to negate A. The negation will strengthen or make the argument valid. Only if there was precipitation every year the age of tree can be determined. If this was not true then there was some other reason for the formation of new rings, and then the entire reasoning of the argument is destroyed. A was correct if 'not' was omitted from A.
I first chose C, because I thought that the central point was to determine the age of the tree regardless the number of times the temperature goes above 95.
But paraphrasing the argument, we could say: "Only when the temperature does not go above 95, we can determine the age of the Brazilian tree". Thus, the answer E is the best. (one more to the error log!)