PrepTest 109

Incorrect. The stimulus never discusses other countries, so this comparison is unwarranted.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
Adults in country X-most-Consume more fat as they get older
Adults in country X-most-% of fat in diet says the same throughout adult life

Answer Anticipation:
This stimulus fairly explicitly brings up concepts of percents and amounts. We're used to seeing Percent vs. Amount issues in questions that deal in flawed arguments, not Must Be True questions, so we have to shift the way we're viewing these to adjust to the question type!

In general, an argument that jumps between discussing percents and amounts is flawed, because a larger percent doesn't necessarily mean a larger amount. After all, there are a lot more people in American than in New Zealand, so a smaller percentage of Americans could represent a larger group than a larger percentage of New Zealanders!

Let's bring that understanding here—that percentages and amounts can shift around what totals you're talking about.

Here, the percent of fat in a diet stays the same despite adults eating more fat. The only way that the percent could say the same despite the amount of fat going up is if the total amount of food—including non-fat parts of the diet—increased. Since that's the only way to reconcile these two pieces of information, let's find an answer stating that adults tend to eat more as they age.

Answer Explanation:
This answer reflects the only way for the amount of fat in a diet to increase while the percent stays the same—if the total amount of food in the diet increases. Since it's the only way to explain the phenomenon in the stimulus, it's the correct answer.

Key Takeaway:
When Must Be True questions bring in concepts that we've seen in flaw-based questions, think about what issues those concepts lead to and see if they can help you make an inference. Here, we saw Percent vs. Amount issues. We know that these can't be jumped between because totals play a role, and bringing that to this question allowed us to make an inference about the total amount of food consumed by adults.

Incorrect. The stimulus never discusses children in country X, so this answer is out of scope.

Incorrect. Variety of food isn't tied to fat content, so this answer is out of scope.

Incorrect. Fat content of diet isn't tied to losing weight. And, if anything, a bigger diet that includes more total fat would likely have the opposite effect!