Which of the following most logically completes the argument?

A new machine for harvesting corn will allow rows to be planted only fifteen inches apart, instead of the usual thirty inches. Corn planted this closely will produce lower yields per plant. Nevertheless, the new machine will allow corn growers to double their profits per acre because __________.

(A) with the closer spacing of the rows, the growing corn plants will quickly form a dense canopy of leaves, which will, by shading the ground, minimize the need for costly weed control and irrigation
(B) with the closer spacing of the rows, corn plants will be forced to grow taller because of increased competition for sunlight from neighboring corn plants
(C) with the larger number of plants growing per acre, more fertilizer will be required
(D) with the spacing between rows cut by half, the number of plants grown per acre will almost double
(E) with the closer spacing of the rows, the acreage on which corn is planted will be utilized much more intensively than it was before, requiring more frequent fallow years in which corn fields are left unplanted

I debated a lot between (A) and (D) on the exam and picked D. But the OA is A. Instructors, can you please tell why D is wrong....I am doing this a lot on the exam. I always narrow it down to final 2 and end up picking the wrong one. Please help....

D is wrong because it does not take the argument into account and the formula Sales – Costs = Profit…

The argument is “the new machine will allow corn growers to double their profits per acre”.

In general, arguments that discuss profits need to be addressed with the formula of Sales – Costs = Profits. Answer choice A attacks the “cost” part of the formula. If the farmer lowers the costs, profits will rise!

All answer choice D really says is that the number of plants will double. You can not assume that sales will double with costs only rising marginally to create double the amount of profits. This might not be the best advice but you can assume D from the statement – if the spacing is cut in half, the number of plants must double.

Hope this helps…

well done, jeffzolman.

also, note that choice (d) contains something that is actually self-evident from the information that's already in the passage.
in other words, if you cut the spacing between rows by 1/2, then by definition you're going to be able to plant about twice as many plants. therefore, (d) is simply a repetition of what's already in the argument, and adds virtually nothing.

Dear all,
i have come across this question and have picked B because i thought it was very logical tht if the plants grow taller, it will help double the profits.

Bt somehow A is seeming better. i.e dense canopy will reduce the weeds.
pls can some1 help explain?

P

the question says that "corns planted this closely will produce lower yields per plant."
this is a fact and should be taken as such.
by saying that the plants will grow taller (and contending that it should be the correct answer) you are presuming that the yield will be more, because all of these plants will get adequate sunlight.

This reasoning is in contradiction to the facts of the question; whereas we need an answer which will counterbalance the situation.

Great explanation, seraphicgirl.

_________________
Jamie Nelson
ManhattanGMAT Instructor

hi instructors,
i know there is no use to challenge the official answer, but somehow i dun find choice A really convincingly complete the argument. i was actually stuck with the specific term of "double" in the original question.

how i see this question is:
the argument is talking about "a lower yield per plant"
answer "D" is talking about "a doubling plant per acre"

because i told myself that the question didn't really mention how "low" the "yield per plant" will be, i took it as slightly lower; also because i was focusing on the term "double" i chose D...

can someone help justify how can we relate answer A to the idea of "double"?

9 days away from the test and i really need to know the subtle difference....thanks!

remember that you don't need to prove the conclusion of the argument -- you just need to pick the statement that adds force to it.
i.e., the exact mathematical content of "double" = x2 is not significant. in fact, the specific numbers in CR problems almost *never* matter; usually, the only thing that matters is relative comparisons -- for instance, quantity #1 is bigger than quantity #2, or quantity #1 is bigger than it was expected to be, etc.

in this passage, the only thing that matters is that the profits are higher than what could be explained by the plant yields. (i.e., there are twice as many plants per acre, but their yield will be depressed -- so the total output won't be twice as much per acre.)
the "2x" doesn't matter; what matters is that this figure is more than would be explained by plant yields alone. therefore, you have to find some other factor, not having to do with plant yield, that would increase profits.

Even if we go mathematically (and this is actually how I eliminated (D)):

Argument says: The spacing will be cut by half, but corn planted this closely will produce lower yields per plant. NEVERTHELESS, profits will double.

(D) says: the number of plants grown per acre will almost double.

Hence, almost doubling (even doubling) of number of plants will not be sufficient to double profits because planted closely, corn will produce lower yields.
One million minus one is not million anymore :)

What (A) does, is that it gives reason why COSTLY expenses will be minimized. This answer choice does not impose any specific constrains as (D) does; hence (A) is better.

this reasoning is workable, but it's still important to understand the warning above about being too "mathematical" in CR.

another thing about this choice is that it's basically nothing -- if the distance between rows is halved, then we already know, by default, that the new # of plants will be approximately twice the old number. so that choice basically just spells out what is already there.