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Tough CR from MGMAT

by netigen » Sun Jun 15, 2008 4:41 pm
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.
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by VerbalAttack » Sun Jun 15, 2008 6:45 pm
Is the OA E?

Here is the reason;

The argument says, "...to help regulate the internal temperature of the tree, the outermost layers of wood of the Brazilian ash often peel away..."

above statement says 'the outermost layers.." but stops short of saying how many layers, so the number of layers affected is unpredictable and hence the difficulty in determining the age of the tree.

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by durgesh79 » Sun Jun 15, 2008 8:23 pm
tough one ....

if we apply negation on E, the statement will be "The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is predictable."

So, if we know that how many times the temp has gone above 95 in past, we can still find out the age of the tree. while the statement says the "only way" is when .........

The problem with this option is, that we are assuming that we know exactly how many times temp has gone above 95 in last 50 or may be 100 years. practically it may not be possible, so the whole process is not reliable......
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by netigen » Sun Jun 15, 2008 8:51 pm
durgesh79 wrote:tough one ....

if we apply negation on E, the statement will be "The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is predictable."

So, if we know that how many times the temp has gone above 95 in past, we can still find out the age of the tree. while the statement says the "only way" is when .........

The problem with this option is, that we are assuming that we know exactly how many times temp has gone above 95 in last 50 or may be 100 years. practically it may not be possible, so the whole process is not reliable......
Exactly my thoughts, we do not know how many times temp went above 95 in the life of the tree.

May be MGMAT experts here can throw some light on this CR Q.
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by loki.gmat » Sun Jun 15, 2008 10:20 pm
here r my thoughts -

A - levels of precipitation - out of scope of the argument. hence incorrect.
B - here we r not talking abt other tress, hence Only the Brazilian ash ........ will not make a difference.hence incorrect.
C - even if two days or three days of temperatures above 95 degrees Fahrenheit is needed to cause the Brazilian ash to lose a ring, it wont make a difference.hence incorrect.
D - the argument clearly says that the tree is losing some of the rings bcoz of high temperature. so the thickness of the remaining rings wont help to measure the tree's age.hence incorrect.

E - assume that we know the number of times the temperature exceeds 95 degrees Fahrenheit. apply the negation i.e,The number of rings that will be lost when the temperature exceeds 95 degrees Fahrenheit is predictable.
in this case we can calculate tree's age n the argument wont hold its ground.
hence IMO E.

the only problem, i feel, is that we have to assume that we know the number of times the temperature exceeds 95 degrees Fahrenheit.

nyways E seems to be a better option than others.

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OA

by ektamatta » Wed Jun 25, 2008 2:30 pm
what is OA?
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by vcb » Wed Jun 25, 2008 8:22 pm
I am not sure if my thinking is going in the correct direction, but here's some food for thought -
In the para, the author is explicitly being ambiguous about the number of layers the tree would lose, by saying "outermost layers"..so can we take it to be an assumption? whereas, the para seems to suggest that every time the temp goes above 95, the tree loses its 'outermost layers'.
What if the temp hovers on the 95 deg border over the day? i mean, 94 at 9AM, 95 at 10AM and so on?would the tree keep losing its bark every hour? :)) Am i getting too snooty here?;))
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by Stacey Koprince » Thu Jul 10, 2008 10:06 am
It is true that we don't know whether we could know how many times the temp goes above 95. But IF there were a way for me to predict what would happen when the temp DOES go above 95, then I couldn't reasonably claim that ONLY if the temp never exceeds 95 can I calculate age based on rings.

But I have made that claim so, at this point, I must be assuming that there is NEVER a way for me to calculate age based on rings when the temp does go above 95. And that's basically what E says.

durgesh79 also points something out: if you negate the statement to say that the number of rings lost IS predictable and toss that sentence up into the argument... it basically kills the claim. Try it:

Rings can be lost when the temp goes above 95.
The # of rings lost in this way is predictable.
Therefore, the ONLY way to calculate reliably is when the temp never exceeds 95.

Huh? You'd be looking at the person saying this with an extremely skeptical expression. :)
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by peter.p.81 » Wed May 11, 2016 12:53 am
I'd say E but I'm afraid more because of my intuition than any logic
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