LSAT Lab: Must Be True Questions in Logical Reasoning

Introduction

• Focus on "must be true" questions in the logical reasoning section.
• These questions make up about 4% of all logical reasoning questions.
• Despite their rarity, they're foundational and often more complex.

Identifying Must Be True Questions

• Look for question stems with phrases like:
  • "must be true"
  • "can be logically inferred"
  • "can be properly concluded"
  • "find a consequence of the view above"
• Watch for question types asking for exceptions, where most answers must be true except for one.

Approach to Must Be True Questions

1. Find Related Statements:
   • Identify common terms linking statements.
   • Consider the reasoning structure.
2. Anticipate the Answer:
   • Use linked terms and reasoning to predict the answer.
3. Evaluate Answers:
   • Work from wrong to right.
   • Use trap answer patterns to eliminate incorrect options.

Example with Conditional Logic

• Conditional Logic is predominant in must be true questions (75%).
• Use transitive property to connect conditional statements:
  • If A -> B and B -> C, then A -> C.
• Example: If K -> M and M -> not P, infer K -> not P.

Example with Comparison

• Comparative Reasoning accounts for 19% of questions.
• Example: If City A is more populous than City B and smaller, then density is greater in City A.
• Be wary of comparisons at different points in time.

Example with Causation

• Although less common, Causal Reasoning can appear.
• Understand causal chains:
  • Sewage -> Pollution -> Algae -> Toxic Organisms -> Fish Die-off.
• Infer forward through the causal chain.

Trap Answer Patterns

1. Scope Traps:
   • Answers that are out of scope or mere speculation.
2. Logical Traps:
   • Unsupported relationships or wrong reasoning types.
3. Opposite Answers:
   • Answers that are the opposite of what’s required.
4. Reversal/Negation Traps:
   • Incorrectly reversing or negating relationships.
5. Support Traps:
   • Answers that support statements rather than infer them.
6. Degree Traps:
   • Overly strong answer choices.

Summary

• Identify with terms like "must be true" or "inferred."
• Be vigilant about conditional logic and minor roles of comparison and causation.
• Avoid trap patterns by focusing on relationship logic and the strength of conclusions.

Resources

• Explore further resources and videos at LSATLab.com for more insights on logical reasoning questions.