LSAT 142 | Section 4 | Logical Reasoning: Q3

LR Question 3 Explanation

QUESTION TEXT: The master plan for the new park calls for the planting…

QUESTION TYPE: Strengthen

CONCLUSION: The donated trees are probably native trees that don’t grow to be very large.

REASONING: The trees come from Three Rivers Nursery, which mostly sells native trees and shrubs.

ANALYSIS: There were two conditions in the master plan:

• The tree is native to the area.
• The tree doesn’t grow very large.

The nursery mostly sells native trees and shrubs, so there’s decent evidence the nursery’s trees are probably native. But we don’t know for sure. We only know that most trees and shrubs are native. But that could be mostly shrubs. For instance, this is a possible breakdown of the nursery’s plants:

• 30% non-native trees.
• 10% native trees.
• 60% native shrubs.

In this example, most of the plants are either native trees or shrubs. But most of the trees are non-native. So we could strengthen the argument by showing that most of the trees themselves are native, which would eliminate possibilities like the one I described above.

The evidence is also missing the other condition. We don’t know how large the nursery’s native trees get. If many nursery trees grow large like cottonwoods do, then the donated trees are no good. We can strengthen the argument by showing the nursery’s trees are small.

Note: It’s not clear whether non-native trees are allowed. “Calls for” usually means that the rules listed are a complete expression of the plan. But it’s possible other rules allow non-native trees. However, this doesn’t matter, since we don’t know what non-native trees comply with the master plan. The only way to prove that the nursery trees comply is for them to be native, since we know what conditions native trees must meet.

___________

1. This answer must be talking about non-native trees. The master plan clearly said that large native trees are no good.
   This answer can’t strengthen anything, because it’s so vague. It could mean that one type of non-native tree not carried by the nursery grows large and is consistent with the plan. That doesn’t help prove anything about nursery trees.
2. This weakens the argument. Cottonwoods grow large, so they’re not consistent with the master plan.
3. This weakens the argument. We only know that native trees are consistent with the master plan. This answer lessens the amount of native trees carried by the nursery. We know that most of what the nursery sells are native trees and shrubs. For instance, 60% of the stock is “native trees and shrubs”. The greater percentage of that 60% that’s shrubs, the smaller the percentage that’s native trees.
4. This weakens the argument, because it reduces the amount of trees that are consistent with the plan. This answer makes it less likely that the nursery carried some allowable non-native trees.
5. CORRECT. This strengthens the argument. The plan doesn’t allow trees that are too large. So this answer shows that the nursery’s native trees will meet the plans requirements: they’re native, and they don’t grow too large.