SSC CGL 2025 Tier-I · 19 September 2025, Shift 3 · General Intelligence and Reasoning · Question 12 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 11 September 2026.

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SSC does not publish CGL question papers or a public answer key. From 2025 the candidate response sheet prints every question and option as a picture, so the text here is transcribed from those pictures for this shift and checked against them independently; where the layout carries meaning, the picture is shown as well. Each answer is the key SSC colour-marked on that sheet. SSC released a tentative key for challenge and later its final one, both only to candidates behind a login, and the sheet does not say which of the two it carries. The solutions are written by UnlockIAS.

Complete the given pattern : 13, 17, 23, 31, 41, ?

(a)47
(b)53
(c)59
(d)61

Answer

Why

Correct — B.
Rule: differences +4, +6, +8, +10, growing by 2 each time.

13 + 4 = 17
17 + 6 = 23
23 + 8 = 31
31 + 10 = 41

Next difference is +12: 41 + 12 = 53 → option (b).

Why the others are wrong

(a)
47 — 47 adds 6 to 41. The differences have been rising, 4, 6, 8, 10, so the next one is 12, not 6.
(c)
59 — 59 adds 18 to 41. The differences grow by 2 each step, so after 10 comes 12, giving 53.
(d)
61 — 61 adds 20, double the last difference. The differences grow by adding 2, not by doubling, so 10 becomes 12.

Concept

When a series climbs by uneven steps, write the differences underneath. Here they are 4, 6, 8, 10, and those themselves rise by a steady 2, a second-level pattern.

Every term in the series is a prime, and so is every option: 47, 53, 59 and 61. So primality cannot pick the answer. The differences can, and 53 is the value that continues them.

The terms are primes but not consecutive primes: 19, 29 and 37 are skipped. So the next prime after 41, which is 43, is not the rule, and 43 is not offered.

Key facts

Differences of 4, 6, 8, 10, 12 give 13, 17, 23, 31, 41, 53.
13, 17, 23, 31, 41 and 53 are all prime, but the series skips the primes 19, 29 and 37.

Study next

Series whose differences grow by a fixed step, such as 3, 5, 7, 9Series built on n² + n, such as 2, 6, 12, 20, 30Series with alternating differences

Common traps

Using primality to choose, when all four options are prime
Repeating the last difference or doubling it instead of adding 2

15 Sep 2025, 16:00, Reasoning Q.18 runs the same differences, +4, +6, +8, +10, on 2, 6, 12, 20, 30, ?, keyed 42.

18 Sep 2025, 12:30, Reasoning Q.11 sets the identical series, keyed 42.

Related PYQs

No directly related past PYQ was found.