Logical Deductions MCQs for MDCAT Practice

Logical Reasoning section, Logical Deductions chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

1. Question 1
   The set of all real numbers under the usual multiplication operation is not a group because?
   • Azero has no inverse. (correct answer)
   • BIdentity element does not exist.
   • CMultiplication is not associative.
   • DBoth A and B.
   Correct answer: A

   The set of real numbers under multiplication fails to form a group primarily because zero lacks a multiplicative inverse, violating a core group axiom.
2. Question 2
   Statements: All boys are honest. Sachin is honest. Conclusions: 1. Sachin is a boy. 2. All honest persons are boys.
   • AOnly conclusion I follows
   • BOnly conclusion II follows
   • CEither I or II follows
   • DNeither I nor II follows (correct answer)
   Correct answer: D

   This question tests the understanding of logical fallacies, specifically the fallacy of the undistributed middle and affirming the consequent in syllogistic reasoning.
3. Question 3
   Fact-Checking.Fact 1: Pictures can tell a story.Fact 2: All storybooks have a picture. Fact 3: Some storybooks have words. If the above three statements are facts, then which of the following statement will also be a fact?I. Pictures can tell a story better than words can. II. The stories in storybooks are simple.Ill. Some storybooks have both pictures and words.
   • AOnly I
   • BOnly II
   • COnly III (correct answer)
   • DNone of them is a fact
   Correct answer: C

   This question tests deductive reasoning, specifically the ability to derive a necessary conclusion from given premises about storybooks, pictures, and words.
4. Question 4
   The use of aversive conditioning techniques is ethically justified in treating certain psychological disorders:
   • ADisagree
   • BSlightly disagree (correct answer)
   • CNeutral
   • DSlightly agree
   • EAgree
   Correct answer: B

   Aversive conditioning has limited but narrow clinical use; strong ethical concerns outweigh broad justification, making 'slightly disagree' the most defensible stance.
5. Question 5
   Statements: All chocolates are tasty. No tasty thing is healthy. Conclusions: I. No chocolate is healthy. II. Some tasty things are healthy.
   • AOnly I (correct answer)
   • BOnly II
   • CBoth
   • DNeither I nor II
   Correct answer: A

   This question tests the ability to deduce logical conclusions from given categorical syllogisms, emphasizing the exclusion principle derived from universal negative statements.
6. Question 6
   If all roses are flowers and some flowers fade quickly, which of the following is correct?
   • AAll roses fade quickly
   • BSome roses fade quickly
   • CSome flowers may not be roses (correct answer)
   • DNo rose fades quickly
   Correct answer: C

   This question tests understanding of syllogistic reasoning and the scope of quantifiers ('all', 'some').
7. Question 7
   Statements: l. All cups are pencils.II. Some pencils are pens.Conclusions: I. Some pencils are cups. II. No pencils are cups. III. Some cups are pens.
   • AOnly conclusion (I) follows (correct answer)
   • BOnly conclusion (II) follows
   • CBoth I and III follow
   • DNeither conclusion follows
   Correct answer: A

   This question tests understanding of categorical syllogisms, specifically the conversion of universal affirmative statements and the fallacy of the undistributed middle.
8. Question 8
   Statement 1: John runs faster than George. Statement 2: Tom runs faster than John. Statement 3: George runs faster than Tom. If 1 and 2 are true, statement 3 is:
   • ATrue
   • BFalse (correct answer)
   • CUncertain
   • DNone of the above
   Correct answer: B

   This question tests deductive reasoning by analyzing comparative statements to determine the truth value of a subsequent statement.

Read the full Logical Deductions chapter notes: Logical Deductions notes. Or browse every chapter.