UPSC Prelims 2026 CSAT Paper II · Q57 of 70 Mental Ability easy

In a sequence of numbers, each number other than the first two is the sum of the two immediately preceding numbers from it. If the first two numbers in the sequence are 4 and 7, then the sixth number is

  1. (a) 29
  2. (b) 37
  3. (c) 43
  4. (d) 47 ✓ UPSC's answer

Why the answer is (d)

• The sequence follows the rule where each term is the sum of the two preceding terms, starting with 4 and 7.

• The third number is 4 + 7 = 11.

• The fourth number is 7 + 11 = 18.

• The fifth number is 11 + 18 = 29.

• The sixth number is 18 + 29 = 47.

• Therefore, the sixth number in the sequence is 47, which corresponds to option (d).

Why the other options are wrong

(a) 29
29 is the fifth number in the sequence, not the sixth.
(b) 37
37 is not a term in this specific Fibonacci-like sequence starting with 4 and 7.
(c) 43
43 is not a term in this specific Fibonacci-like sequence starting with 4 and 7.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2026, held on 24 May 2026. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

Reading the answer is not the same as getting it right under a clock. Practise this question with UPSC's negative marking, and anything you miss goes into an error notebook until you get it right twice.

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