LSAT 159 | Section 1 | Logical Reasoning: Q18

LR Question 18 Explanation

QUESTION TEXT: Putting a tap in a healthy maple that has a trunk 12 or more inches …

QUESTION TYPE: Must Be True

FACTS:

1. Tapping does not harm a healthy maple if the trunk is 12+ inches in diameter.
2. Several species can be tapped for syrup.
3. Sugar maple is best for syrup because its sap has the most sugar.

ANALYSIS: The last two statements don’t really give us anything to work with. Presumably, all trees can be tapped for syrup, it’s just a matter of whether tapping will harm it or not. And we don’t know how producing the best syrup relates to anything else.

There’s only one statement that’s logically forced here.

• First sentence: If healthy AND 12+ inches -> tapping will not harm
• Contrapositive: If tapping harms -> not healthy OR not 12+ inches

That’s the only thing we can definitely conclude.

___________

1. CORRECT. This is the contrapositive of the first sentence. Normally, healthy trees over 12 inches can be tapped without harm. So, IF there is harm, then either the tree was not over 12 inches or wasn’t healthy.
    
   Since this answer is talking only about trees over 12 inches, then the only thing left is that they weren’t healthy.
2. The size only relates to whether tapping harms the tree, not the overall health ranking. Watch out for answers with “healthiest”, we rarely get evidence that lets us prove most healthy in a group.
3. We’re not told anything about the relationship between harm and sap quantity.
4. This says: If unhealthy AND less than 12 inches -> tapping will harm. We can’t conclude that based on the first sentence: it told us about trees 12 inches or greater in diameter. It did NOT tell us anything about trees under 12 inches.
5. We just know the author thinks the sugar maple is the best. Not that it’s the most common. In a lot of areas, the best option may be the most expensive and therefore not the most common.