UPSC Prelims 2021·CSAT·Logical Reasoning·Series and Sequences

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?

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Last updated 8 Jul 2026, 4:39 pm IST
  1. A2.5
  2. B5
  3. C9.375Correct
  4. D32.8125

Explanation

The pattern in Sequence-I needs to be identified first. Let's look at the ratio of consecutive terms in Sequence-I:

  1. 4 / 8 = 0.5
  2. 6 / 4 = 1.5
  3. 15 / 6 = 2.5
  4. 52.5 / 15 = 3.5
  5. 236.25 / 52.5 = 4.5

The multipliers are 0.5, 1.5, 2.5, 3.5, 4.5. This is an arithmetic progression with a common difference of 1.

Now, apply this same pattern to Sequence-II, which starts with 5. Sequence-II: 5, A, B, C, D, E

  1. A = 5 * 0.5 = 2.5
  2. B = A * 1.5 = 2.5 * 1.5 = 3.75
  3. C = B * 2.5 = 3.75 * 2.5 = 9.375

Therefore, the entry in the place of C is 9.375.

Analyzing the options: A) 2.5: This is the value of A, not C. B) 5: This is the starting term of Sequence-II. C) 9.375: This matches our calculated value for C. D) 32.8125: This would be the value of D (C * 3.5 = 9.375 * 3.5 = 32.8125).

The final answer is C.

Logical Reasoning: You are given two identical sequences in two rows: +--------------+----+----+----+------+-------+--------+ | Sequence-I
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