UPSC Prelims 2017·CSAT·Logical Reasoning·Arrangement and Puzzles

Consider the following: A, B, C, D, E, F, G and H are standing in a row facing North. B is not neighbour of G. F is to the immediate right of G and neighbour of E. G is not at the extreme end. A is sixth to the left of E. H is sixth to the right of C. Which one of the following is correct in respect of the above?

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  1. AC is to the immediate left of A
  2. BD is immediate neighbour of B and F
  3. CG is to the immediate right of DCorrect
  4. DA and E are at the extreme ends.

Explanation

Let's reconstruct the arrangement step-by-step: 1. "F is to the immediate right of G and neighbour of E." This implies a block: G F E. 2. "A is sixth to the left of E." This means there are 5 people between A and E. Combining with the GFE block, we get: A _ _ G F E. This accounts for 6 positions. 3. Since there are 8 people in total, and A is at the leftmost position in this partial arrangement, the full arrangement starts with A: A _ _ G F E _ _. So, A is at position 1, G at 4, F at 5, E at 6. 4. "G is not at the extreme end." This is satisfied as G is at position 4. 5. "H is sixth to the right of C." This means there are 5 people between C and H: C _ _ _ _ H. Given our partial arrangement A _ _ G F E _ _, the only way to fit C and H such that H is 6th to the right of C is if C is at position 2 and H is at position 8. So, the arrangement becomes: A C _ G F E _ H. 6. The remaining people are B and D. The remaining slots are 3 and 7. Two possibilities: a) A C B G F E D H b) A C D G F E B H 7. "B is not neighbour of G." a) In A C B G F E D H, B is immediately to the left of G, making B a neighbour of G. This option is invalid. b) In A C D G F E B H, D is immediately to the left of G, and F is immediately to the right of G. B is at position 7, not next to G. This option is valid. Therefore, the final arrangement is: A C D G F E B H. Now let's check the options: A) C is to the immediate left of A. In A C D G F E B H, C is to the immediate right of A. (Incorrect) B) D is immediate neighbour of B and F. In A C D G F E B H, D's neighbours are C and G. F's neighbours are G and E. B's neighbours are E and H. (Incorrect) C) G is to the immediate right of D. In A C D G F E B H, D is at position 3 and G is at position 4. So, G is to the immediate right of D. (Correct) D) A and E are at the extreme ends. In A C D G F E B H, A is at the left extreme end (position 1), but H is at the right extreme end (position 8), not E (which is at position 6). (Incorrect) The final answer is C
Logical Reasoning: Consider the following: A, B, C, D, E, F, G and H are standing in a row facing North. B is not neighbour of G. F is to t

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