GMAT Weaken CR: Percentage vs Number | OG | Cantaria

The Official GMAT question that begins “Fast-food restaurants make up 45 percent of all restaurants in Cantaria” shows how a hidden conversion from percentage to absolute number can decide a Weaken question.

A share falls, so the absolute number must fall too.

Not necessarily, right?

Yet while solving questions, many of us make that jump without noticing, and many GMAT arguments rely on it. When the evidence is about a percentage and the conclusion is about an absolute number, or the other way around, the argument has a hidden step. That step is often where the correct answer hits.

The jump is easy to miss because it never appears as a sentence in the argument. The author states the percentages, states the conclusion, and the conversion happens silently in between. The habit to build is to find where the argument moves from one to the other and ask what that move needs.

The question

Here is an easy Official question that shows this clearly.

In a country called Cantaria, fast-food restaurants make up 45% of all restaurants. Their customers tend to be young, and studies show that the older people get, the less likely they are to eat at these restaurants. The average age of the population is gradually rising and is expected to keep rising. The author concludes that the number of fast-food restaurants is likely to decrease.

The reasoning looks straightforward. Older people are less likely to eat fast food. The population is getting older. So fewer people will eat fast food, demand will fall, and fewer restaurants will survive.

Where the argument jumps

The conclusion is about a number: how many fast-food restaurants there will be. The evidence is about shares and likelihoods. Older people are less likely to eat fast food, and a rising average age means older people are becoming a larger share of the population.

None of this is a count of customers. To reach the conclusion, the author jumps from “young people will be a smaller share of the population” to “there will be fewer young customers, and fewer customers overall.” That jump holds only if the total population stays roughly the same.

So, the correct choice needs to give you a reason to believe that the number of fast-food customers may not fall, even though the population is getting older.

The correct choice

The correct choice tells you that the overall population of Cantaria is growing steadily.

Run the numbers:

Today Some years later

Young people 50 50

Older people 50 100

Total population 100 150

Share of older people 50% 67%

The share of older people has risen, so the average age has gone up, exactly as the passage says.

But the number of young people has not fallen at all.

And the older group, though less likely per person to eat fast food, is now twice as large. The number of fast-food customers may not drop, and if demand holds, the number of restaurants may not drop either.

Notice that this choice does not contradict any premise. The average age still rises, and older people are still less likely to eat fast food. It breaks only the hidden step from a smaller share to a smaller number.

It also does not prove that the number of restaurants will stay the same. It makes the author’s prediction less certain, and that is all a weakener needs to do.

This is the choice students eliminate as irrelevant. It says nothing about fast food, eating habits, or age, yet it is the one fact the argument quietly depends on.

Modified Conclusion

Now change the conclusion. Suppose the author had concluded that

"a smaller proportion of Cantarians will eat at fast-food restaurants."

Does a growing population weaken this conclusion?

No. A proportion does not depend on the size of the total.

If older people are less likely to eat fast food and they make up a larger share of the population, a smaller proportion of people will eat fast food whether the population grows or not.

So, population growth weakens the original conclusion only because that conclusion is about a number. The type of claim decides what can weaken it.

Can you think of a choice that would weaken the modified conclusion?

Quick checklist

Before you reject a choice in a question that mixes percentages and numbers, ask yourself:

Is the conclusion about a number, a share, or a rate?
Is the evidence about the same thing?
If not, what must be true for the conversion to work?

Percentages and absolute numbers are not interchangeable. The conversion between them is never automatic, and GMAT tests that gap in Weaken, Strengthen, Assumption, and Inference questions alike.

About the Weaken Beginner Series

This question is part of the free Weaken Beginner Series, in which easy Official GMAT questions are used not to test what you know, but to reveal how you think. Each question targets a specific reasoning habit, one that shows up in a simple form on easy questions and a complex one on hard questions. If you are getting started with Weaken questions or if Weaken questions feel inconsistent for you, this series is built to show you exactly where the process is breaking down.

Solve the question on your own first. The reasoning you apply matters more than the answer you reach.

Noticing a hidden conversion is easier once you know which step of your process tends to slip.

Percentage-Absolute Number Conversion: The Subtle Gap Tested Across CR Question Types