LSAT 5 | Section 3 | Logical Reasoning: Q12

LR Question 12 Explanation

QUESTION TEXT: The number of North American children who are obese…

QUESTION TYPE: Must be True

ANALYSIS: This almost counts as a trick question. It perfectly illustrates the difference between absolute numbers vs. rates/percentages. That difference is a key LSAT theme.

Obesity is defined as the children who are heavier than 85% of other children. In other words, the top 15% of children are obese, by this definition. It doesn’t matter if children weigh 100 pounds or 400 pounds on average: the top 15% are obese. That percentage cannot increase. (This is an absurd way to define obesity. You would have “obesity” even if no one was actually fat)

But the number of obese children can increase, and it did. If obese children increased from 15 million to 20 million, that would be an increase in number.

The percentage of obese children always stays constant. So if the number of obese children increases, then the number of non-obese children has to increase. That is the only way that the ratios will stay the same.

___________

1. Not necessarily true. The studies could all be terribly wrong.
2. Who knows? We’re not told why there are more obese children.
3. CORRECT. Yes. This is the only way to keep the ratios constant.
4. This cannot be true, since then the ratio of obese to non-obese children would change.
5. We’re not told anything about the age of obese children.

Recap: The question begins with “The number of North American children who are obese”. It is a Must be True question. Learn more about LSAT MBT questions in our guide to LSAT Logical Reasoning question types.