When feeding

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akhpad: Legendary Member; Posts: 809; Joined: Wed Mar 24, 2010 10:10 pmFollowed by: 4 members; Thanked: 50 times

by akhpad » Sat Oct 16, 2010 3:02 am

Source: GMAT Prep

When feeding, aquatic birds known as phalaropes often spin rapidly on the water's surface, pecking for food during each revolution.To execute these spins, phalaropes kick one leg harder than the other.This action creates upwelling currents.Because plankton on which phalaropes feed typically occurs in greater quantities well below the surface, it is hypothesized that by spinning phalaropes gain access to food that would otherwise be beyond their reach.

Which of the following, if true, most strongly supports the hypothesis?

A. Phalaropes rarely feed while on land.
B. A given phalarope spins exclusively either to the right or to the left.
C. Phalaropes sometimes spin when they are not feeding.
D. Different phalaropes spin at somewhat different rates.
E. Phalaropes do not usually spin when food is abundant at the surface.

OA: E

Source: Beat The GMAT — Critical Reasoning | Sat Oct 16, 2010 3:02 am

diebeatsthegmat: Legendary Member; Posts: 1119; Joined: Fri May 07, 2010 8:50 amFollowed by: 3 members; Thanked: 29 times

by diebeatsthegmat » Sat Oct 16, 2010 9:06 am

akhpad wrote:Source: GMAT Prep

When feeding, aquatic birds known as phalaropes often spin rapidly on the water's surface, pecking for food during each revolution.To execute these spins, phalaropes kick one leg harder than the other.This action creates upwelling currents.Because plankton on which phalaropes feed typically occurs in greater quantities well below the surface, it is hypothesized that by spinning phalaropes gain access to food that would otherwise be beyond their reach.

Which of the following, if true, most strongly supports the hypothesis?

A. Phalaropes rarely feed while on land.
B. A given phalarope spins exclusively either to the right or to the left.
C. Phalaropes sometimes spin when they are not feeding.
D. Different phalaropes spin at somewhat different rates.
E. Phalaropes do not usually spin when food is abundant at the surface.

OA: E

the CR concluded that the fish spin to reach food beyond their reach. it means that they hardly rotate around then the plankton will be able to float on the surface and the fishes can eat the food
why they do that? the assumption is just because they dont have much food around...
so E can weaken it

this_time_i_will: Master | Next Rank: 500 Posts; Posts: 268; Joined: Wed Mar 17, 2010 2:32 am; Thanked: 17 times

by this_time_i_will » Sat Oct 16, 2010 9:40 am

diebeatsthegmat wrote:
akhpad wrote:Source: GMAT Prep

When feeding, aquatic birds known as phalaropes often spin rapidly on the water's surface, pecking for food during each revolution.To execute these spins, phalaropes kick one leg harder than the other.This action creates upwelling currents.Because plankton on which phalaropes feed typically occurs in greater quantities well below the surface, it is hypothesized that by spinning phalaropes gain access to food that would otherwise be beyond their reach.

Which of the following, if true, most strongly supports the hypothesis?

A. Phalaropes rarely feed while on land.
B. A given phalarope spins exclusively either to the right or to the left.
C. Phalaropes sometimes spin when they are not feeding.
D. Different phalaropes spin at somewhat different rates.
E. Phalaropes do not usually spin when food is abundant at the surface.

OA: E
the CR concluded that the fish spin to reach food beyond their reach. it means that they hardly rotate around then the plankton will be able to float on the surface and the fishes can eat the food
why they do that? the assumption is just because they dont have much food around...
so E can weaken it

E supports/strengthens the argument, not weakens it.

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akhpad: Legendary Member; Posts: 809; Joined: Wed Mar 24, 2010 10:10 pmFollowed by: 4 members; Thanked: 50 times

by akhpad » Sat Oct 16, 2010 10:07 pm

Above explanation might be correct but I am unable to understand stimulus. What is going on?

Can someone explain?

ov25: Master | Next Rank: 500 Posts; Posts: 201; Joined: Sat Jul 10, 2010 2:23 pmFollowed by: 1 member; Thanked: 7 times

by ov25 » Sun Oct 17, 2010 5:15 am

Arg: spinning helps reach pl well below surfaces for food. they use currents, kick one leg harder and reach bottom

A:feeding on land - out of scope
B: spins only right or left...does not matter as long as either helps it to reach down below
C: weakens: spins when not feeding...obv. not necessarily helping feed every time
D: same as B - does not matter how fast they spin
E: Strengthens: Ah hah! when abundant food exists in the same plan, don't have to reach down below

gmat_perfect: Legendary Member; Posts: 1083; Joined: Wed Feb 24, 2010 9:38 pmFollowed by: 14 members; Thanked: 127 times

by gmat_perfect » Sun Oct 17, 2010 6:06 am

akhpad wrote:Source: GMAT Prep

When feeding, aquatic birds known as phalaropes often spin rapidly on the water's surface, pecking for food during each revolution.To execute these spins, phalaropes kick one leg harder than the other.This action creates upwelling currents.Because plankton on which phalaropes feed typically occurs in greater quantities well below the surface, it is hypothesized that by spinning phalaropes gain access to food that would otherwise be beyond their reach.

Which of the following, if true, most strongly supports the hypothesis?

A. Phalaropes rarely feed while on land.
B. A given phalarope spins exclusively either to the right or to the left.
C. Phalaropes sometimes spin when they are not feeding.
D. Different phalaropes spin at somewhat different rates.
E. Phalaropes do not usually spin when food is abundant at the surface.

OA: E

General strategy for strengthening questions:

The following steps will help to master the strengthening questions:

Step1: Identify the necessary ASSUMPTION. --At least imagine an assumption.

Application: The conclusion is the by spinning phalaropes gain access to food that would otherwise be beyond their reach.

What assumption led the author to conclude this?

The potential assumptions:
1. Phalaropes do not spin when they do not need to eat.
2. Phalaropes are nto required to spin for any other purpose.
3. No one has seen phalaropes to spin when they are not near the food.
4. If there are lot of food available surrounding them, they usually do not spin.

Any one of these assumption has been assumed by the author to reach the conclusion.

Step2: Attack the choices.

The choice E matches with one of the assumed assumptions.

Answer is E.

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