Mexico City has a serious water problem. Situated in a high, enclosed mountain bowl, the city relies on groundwater for...

GMAT Critical Reasoning : (CR) Questions

Source: Mock

Critical Reasoning

Weaken

MEDIUM

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Mexico City has a serious water problem. Situated in a high, enclosed mountain bowl, the city relies on groundwater for more than 80 percent of its supply. Pumping exceeds natural replenishment, so the depleted ground is subsiding, causing damage to buildings. Much water is lost to users, however, through leaks in the aging water-distribution system. Repairs would therefore increase the available supply without the damage that increased pumping would cause.

Which of the following, if true, is a consideration that weakens the argument given?

At some locations in the city, water use is not metered and cannot be billed to individual households.

The city has an extensive program of providing household water-saving devices at no direct cost to households.

Bringing water to the city from the nearest river, 80 miles away beyond the mountains, is extremely costly.

Water demand per person is falling, but migration is increasing the number of people in the city.

Water leaked from the water-distribution system seeps down, reaching the level of the groundwater.

Solution

Passage Analysis:

Text from Passage	Analysis
Mexico City has a serious water problem.	What it says: Mexico City is facing major water issues What it does: Sets up the main problem we're going to discuss What it is: Author's opening claim
Situated in a high, enclosed mountain bowl, the city relies on groundwater for more than 80 percent of its supply.	What it says: The city's location makes it heavily dependent on underground water (80%+) What it does: Explains the geographic reason behind the water problem What it is: Background information/context Visualization: Mexico City gets 80+ out of every 100 water units from underground sources
Pumping exceeds natural replenishment, so the depleted ground is subsiding, causing damage to buildings.	What it says: They're taking out more water than nature puts back, making the ground sink and harming buildings What it does: Shows the specific consequences of over-pumping groundwater What it is: Cause-and-effect explanation Visualization: \(\mathrm{Water\ going\ out} > \mathrm{Water\ coming\ in}\) = Ground sinking down
Much water is lost to users, however, through leaks in the aging water-distribution system.	What it says: A lot of water gets wasted because the old pipes have leaks What it does: Introduces a separate issue that adds to the water shortage problem What it is: Additional problem factor
Repairs would therefore increase the available supply without the damage that increased pumping would cause.	What it says: Fixing the leaky pipes would give more water without the harmful effects of pumping more What it does: Presents the author's solution by connecting pipe repairs to avoiding pump damage What it is: Author's main conclusion/recommendation

Argument Flow:

The argument starts with a problem (water shortage), explains the geographic cause (mountain location + groundwater dependence), shows the consequences of the current solution (over-pumping damages buildings), identifies an additional issue (leaky pipes waste water), and then proposes a better solution (fix pipes instead of pump more).

Main Conclusion:

Repairing Mexico City's leaky water pipes would solve the water shortage without causing the building damage that comes from increased groundwater pumping.

Logical Structure:

The author uses a problem-solution structure: establishing that over-pumping causes building damage, showing that leaks waste water, then concluding that fixing leaks is better than pumping more because it increases supply without the negative side effects.

Prethinking:

Question type:

Weaken - We need to find information that would reduce our belief in the conclusion that repairs would increase available supply without the damage from increased pumping

Precision of Claims

The author makes specific claims about quantity (80% groundwater reliance, much water lost through leaks) and causality (repairs will increase supply without pumping damage). We need to respect these facts but find scenarios that undermine the reasoning

Strategy

Look for scenarios that either:

Show repairs won't actually increase available supply as much as expected
Reveal hidden costs or problems with repairs, or
Suggest the repair solution has drawbacks that weren't considered

We can't contradict the facts (like that leaks exist or that pumping causes subsidence), but we can introduce new information that makes the proposed solution less attractive or effective

Answer Choices Explained

At some locations in the city, water use is not metered and cannot be billed to individual households.

This choice tells us that some water use isn't metered or billed. However, this doesn't weaken the argument about repairs increasing supply. Whether water is metered or not doesn't change the fact that fixing leaks would prevent water loss. The billing system is irrelevant to the physical relationship between repairs and water supply.

The city has an extensive program of providing household water-saving devices at no direct cost to households.

This choice mentions the city providing water-saving devices at no cost. While this shows the city is trying other conservation methods, it doesn't weaken the argument that repairs would be beneficial. If anything, it might suggest the city is already taking comprehensive steps to address the water problem, but it doesn't undermine the logic that fixing leaks would increase supply.

Bringing water to the city from the nearest river, 80 miles away beyond the mountains, is extremely costly.

This choice discusses the high cost of bringing water from a distant river. However, this actually supports rather than weakens the argument for repairs. If importing water is extremely costly, then fixing leaks to increase available supply becomes an even more attractive alternative. This makes the repair solution look better, not worse.

Water demand per person is falling, but migration is increasing the number of people in the city.

This choice presents competing trends - falling per-person demand but increasing population. While this affects total water demand, it doesn't weaken the core argument that repairs would increase supply without pumping damage. The repair solution would still provide benefits regardless of whether demand is rising or falling.

Water leaked from the water-distribution system seeps down, reaching the level of the groundwater.

This choice reveals that leaked water 'seeps down, reaching the level of the groundwater.' This significantly weakens the argument because it means the leaked water isn't truly lost - it's returning to the groundwater that supplies 80% of the city's water. If leaked water naturally replenishes the groundwater, then fixing leaks wouldn't increase the total available supply as much as the argument assumes. The water is essentially recycling itself back into the system.

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