UPSC Prelims 2016 · CSAT
Question 12: Logical Reasoning and Mental Ability
Five people A, B, C, D and E are seated about a round table. Every chair is spaced equidistant from adjacent chairs. (i) C is seated next to A (ii) A is seated two seats from D (iii) B is not seated next to A On the basis of above information, which of the following must be true ?
- 1.D is seated next to B
- 2.E is seated next to A
- 3.D and C are separated by two seats
Select the correct answer using the code given below :
AnswerUPSC’s answer is (b).
Put A at seat 0 of a circle of five and C at seat 1 (the mirror case gives the same result). D is two seats from A, so D is at seat 2 or 3. B is not next to A, so B is also at seat 2 or 3. That leaves E at seat 4, next to A (statement 2 true). B and D fill seats 2 and 3, which are adjacent (statement 1 true). D can sit right next to C, so statement 3 need not hold.
- 1. B and D take the two seats away from A's neighbours, so they sit together.
- 2. E is the only person left for the seat next to A.
- 3. D may sit next to C, so they need not be separated by two seats.
Why each option is right or wrong
- (a) Statement 2 is also true, so 1 alone is incomplete.
- (b) Right: D next to B and E next to A hold in every valid seating.
- (c) Statement 3 fails when D sits next to C.
- (d) Statements 1 and 2 must be true.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2016, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.