SSC CGL 2025 Tier-I · 18 September 2025, Shift 1 · General Intelligence and Reasoning · Question 25 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 13 September 2026.

Where this paper and its answers come from

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.

The series given below contains a sequence of numbers. Accordingly identify the incorrect combination 4 , 5 , 14 , 14 , 34 , 36 , 74 , 68

(a)74
(b)34
(c)36
(d)68

Answer

Why

Correct — C.
Rule: two series interleaved, each with a doubling difference.

Odd places: 4, 14, 34, 74 → +10, +20, +40 ✓
Even places: 5, 14, 36, 68 → +9, +22, +32 ✗

With +9, +18, +36: 5, 14, 32, 68
So 36 should be 32 → option (c).

Why the others are wrong

(a)
74 — 74 fits the odd-place series 4, 14, 34, 74: the gaps +10, +20, +40 double each time, and 34 + 40 = 74.
(b)
34 — 34 is the third term of the odd-place series, and 14 + 20 = 34 keeps its gaps doubling (+10, +20). It is correct as printed.
(d)
68 — 68 looks wrong only against the printed 36. From the corrected 32, 32 + 36 = 68, so it fits once 36 is fixed.

Concept

When a series zig-zags (4, 5, 14, 14, 34, 36 …), split it into odd-place and even-place terms and treat them as two series.

Here both halves grow by a doubling difference. The odd places go +10, +20, +40 cleanly. In the even places, changing the single term 36 to 32 restores +9, +18, +36 on both sides of it.

Why not 68? Replacing 68 alone would leave 14 → 36, a gap of +22, still broken. Changing 36 to 32 fixes both its gaps, +18 before and +36 after.

Key facts

Odd places: 4, 14, 34, 74, with gaps +10, +20, +40.
Even places, corrected: 5, 14, 32, 68, with gaps +9, +18, +36.
A wrong term spoils the gaps on both sides of it.

Study next

Interleaved series with a ×3 half and a +3 halfWrong-number series where each term is ×2 plus a constantSeries asking for two wrong terms at once

Common traps

Testing 68 against the printed 36 and marking 68 wrong
Reading the eight numbers as one series: the gaps +1, +9, 0, +20 hide the two patterns

22 Sep 2025, 09:00, Reasoning Q.25 interleaves a ×3 series (4, 12, 36, 108) with a +3 series (9, 12, 15, 18, 21 once corrected) and keys 16, 323 as the wrong pair.

19 Sep 2025, 16:00, Reasoning Q.25 uses the same incorrect-combination wording on 5, 8, 16, 19, 39, 41, 81, keyed 39, 81.

Related PYQs

No directly related past PYQ was found.

Topic: Number Series — all 178 SSC CGL questions on it, every solved shift.