You are given two identical sequences in two rows : Sequence-I : 8, 4, 6, 15, 52·5, 236·25 Sequence-II : 5, A, B, C, D, E What is the entry in the place of C for the Sequence-II ?
- (a) 2·5
- (b) 5
- (c) 9·375 ✓ UPSC's answer
- (d) 32·8125
Why the answer is (c)
• Identify the pattern in Sequence-I: 8 × 0.5 = 4; 4 × 1.5 = 6; 6 × 2.5 = 15; 15 × 3.5 = 52.5; 52.5 × 4.5 = 236.25.
• The multipliers follow the arithmetic progression: 0.5, 1.5, 2.5, 3.5, 4.5 (increasing by 1 each step).
• Apply the first multiplier to Sequence-II: 5 × 0.5 = 2.5 (This is A).
• Apply the second multiplier to A: 2.5 × 1.5 = 3.75 (This is B).
• Apply the third multiplier to B: 3.75 × 2.5 = 9.375 (This is C).
• Therefore, the entry in the place of C is 9.375, which corresponds to option (c).
Why the other options are wrong
- (a) 2·5
- 2.5 is the value of A (the second term), not C.
- (b) 5
- 5 is the starting value of Sequence-II, not the calculated value for C.
- (d) 32·8125
- 32.8125 is the value of D (the fifth term), calculated as 9.375 × 3.5.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2021, held on 10 October 2021. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.