What is the value of X in the sequence 20, 10, 10, 15, 30, 75, X?
- (a) 105
- (b) 120
- (c) 150
- (d) 225 ✓ UPSC's answer
Why the answer is (d)
• The sequence follows a pattern where each term is multiplied by an incrementing factor: 0.5, 1, 1.5, 2, 2.5, 3.
• 20 × 0.5 = 10
• 10 × 1 = 10
• 10 × 1.5 = 15
• 15 × 2 = 30
• 30 × 2.5 = 75
• The next factor is 3, so 75 × 3 = 225.
• Therefore, X = 225, which corresponds to option (d).
Why the other options are wrong
- (a) 105
- 105 is incorrect because it does not result from multiplying 75 by the next logical factor of 3.
- (b) 120
- 120 is incorrect because it does not follow the established multiplication pattern of increasing factors by 0.5.
- (c) 150
- 150 is incorrect because it would imply a factor of 2, which was already used in the previous step.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2022, held on 5 June 2022. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.