LSAT 149 | Section 4 | Logical Reasoning: Q1

LR Question 1 Explanation

QUESTION TEXT: Dentist: I recommend brushing one’s teeth after every…

QUESTION TYPE: Paradox

PARADOX: You should brush your teeth after every meal to remove sugar. Sugars cause cavities. Yet if you can’t brush your teeth, you should chew gum, even if it contains sugar. This will reduce cavities.

ANALYSIS: Gum reduces cavities, even though it contains sugar, which increases cavities. So there must be something the gum does that reduces cavities even more than sugar increases them.

It’s possible gum is good even though it has one bad effect (sugar). We tend to forget that something can be good even if it has flawed.
Don’t be a perfectionist.

Two of the answers just show why gum is not bad. Remember, you’re trying to prove that gum is good. “Not bad” and “good” are not the same thing. One answer talks about improved oral health. But the conclusion is specifically about cavities.

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1. This doesn’t explain why gum is good. At best, a lower sugar content explains why gum is less bad. The dentist wouldn’t tell you to eat plain sugar to cure cavities, even if the amount was small. Sugar, by itself, is harmful.
2. This answer isn’t helpful. It doesn’t tell us why chewing gum can prevent cavities. It just tells us we can fix some cavities. 
3. CORRECT. The stimulus said cavities happen when enamel is demineralized. Chewing gum remineralizes enamel.
    
   So gum protects teeth, even though one part of gum (sugar) harms teeth.
4. This tells us that gum isn’t necessarily harmful. As long as you brush your teeth within 24 hours, you should be ok. But this answer doesn’t tell us why gum is helpful. 
5. This is tempting. But the conclusion is that gum will reduce cavities. This answer talks about contributing to the health of the oral tract. That’s too broad. We need to show gum helps cavities.