LSAT (Law School Admission Test)Analytical ReasoningMedium
A university is scheduling five final exams—Chemistry (C), History (H), Math (M), Physics (P), and Sociology (S)—over five consecutive days, Monday through Friday. Each exam is scheduled for exactly one day, and no two exams share the same day. The following conditions must be met: * History must be scheduled on Wednesday. * Chemistry must be scheduled on a day immediately before or immediately after Math. * Physics cannot be scheduled on Friday. * Sociology must be scheduled on one of the first two days. If Math is scheduled on Thursday, which of the following must be true?
- APhysics is scheduled on Tuesday.
- BChemistry is scheduled on Friday.
- CSociology is scheduled on Monday.
- DChemistry is scheduled on Tuesday.
Show answer & explanationAnswer & explanation
Correct answer: B. Chemistry is scheduled on Friday.
Given that Math is on Thursday, and Chemistry must be immediately before or after Math, Chemistry must be on Wednesday or Friday. Since History is fixed on Wednesday, Chemistry cannot be on Wednesday, leaving Friday as its only option. This is a direct deduction.
Why the other options are wrong
- A. Physics could be on Monday or Tuesday. It does not have to be Tuesday.
- C. Sociology could be on Monday or Tuesday. It does not have to be Monday.
- D. Chemistry cannot be on Tuesday because if Math is Thursday, Chemistry must be Wednesday or Friday. Also, if Chemistry were Tuesday, it wouldn't be next to Math.
Must Be True Deduction
Identifying a statement that is necessarily true based on a specific premise and the given rules, eliminating all other possibilities.
- Start with the given premise.
- Apply all relevant rules to the premise.
- Look for a consequence that cannot be otherwise.
Memory trick: Chains of Logic: Every link leads to the truth.