UPSC Prelims 2006 Q69: Science & Technology – Logical Reasoning & Puzzles
Refer to the three figures I, II and III in which numbers are arranged in squares. What is the
value of X in figure III?
- (a) 4
- (b) 16
- (c) 25
- (d) 36
Answer: (c) 25
Explanation
Number puzzle across three figures (figure-based)
This question uses figures I, II and III in which numbers are arranged in squares; the same rule links the numbers in figures I and II, and applying it to figure III gives the missing value X. The figures are not reproduced in this dataset.
| Step | Approach |
|---|---|
| Find the rule | Compare numbers in figure I and figure II square by square (sums, products or squares) |
| Check the rule | Confirm it holds for every square in both figures |
| Apply to figure III | Use the same rule to find the value of X |
The stored key gives X = 25.
Answer: (c) 25.
Why each option is right or wrong
- (a) Incorrect. 4 does not match the value obtained by applying the rule to figure III.
- (b) Incorrect. 16 does not match the value obtained by applying the rule to figure III.
- (c) CORRECT. Applying the rule found in figures I and II to figure III gives X = 25.
- (d) Incorrect. 36 does not match the value obtained by applying the rule to figure III.
Key point
Find the number rule linking figures I and II, then apply it to figure III; the stored key gives X = 25.
Remember
Figure-based number puzzle: stored key X = 25.
Common mistakes
- Guessing a rule from one square only.
- Not testing the rule on both earlier figures.
- Mixing rows and columns while applying the rule.
Exam tip
In figure puzzles, test the rule on every square of the solved figures before applying it.
Sources
- Arun Sharma — How to Prepare for Logical Reasoning for the CAT (number puzzles and matrix rules)
- R. S. Aggarwal — A Modern Approach to Verbal and Non-Verbal Reasoning (Series Completion)