SSC CGL 2025 Tier-I · 15 September 2025, Shift 1 · General Intelligence and Reasoning · Question 5 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.

What will come at the place of question mark? 1, 2, 6, 21, 88, ?

(a)445
(b)441
(c)443
(d)440

Answer

Why

Correct — A.
Rule: multiply by 1, 2, 3, 4 … and add the same number.

1 × 1 + 1 = 2
2 × 2 + 2 = 6
6 × 3 + 3 = 21
21 × 4 + 4 = 88

Next: 88 × 5 + 5 = 440 + 5 = 445 → option (a).

Why the others are wrong

(b)
441 — 441 is 88 × 5 + 1. The added number grows with the multiplier, +1, +2, +3, +4, so this step adds 5, not 1.
(c)
443 — 443 is 88 × 5 + 3. The multiplication is right but the addition falls short: this step's multiplier and addend are both 5.
(d)
440 — 440 is 88 × 5 with nothing added. Every earlier step adds its multiplier, so the +5 is missing.

Concept

When the terms grow faster and faster, test multiplication before differences. The differences here, 1, 4, 15 and 67, show no clean pattern.

Try multiplying by the step number and adjusting: ×1 turns 1 into 1, and +1 makes 2. ×2 turns 2 into 4, and +2 makes 6. The adjustment always equals the multiplier, which gives ×n + n.

The same rule can be written as (term + 1) × n: (1 + 1) × 1 = 2, and (88 + 1) × 5 = 445. Either form gives the same answer.

Key facts

Rule: next term = term × n + n, for n = 1, 2, 3, 4, 5.
Equivalent form: (term + 1) × n.
Differences 1, 4, 15, 67 have no simple pattern, which points to a multiplying rule.

Study next

Series with a growing multiplier and a fixed addition (×2 + 1, ×3 + 1 …)Wrong-term series built on a ×n + n ruleSeries mixing squares or cubes with a fixed addition

Common traps

Stopping at 88 × 5 = 440 and forgetting the addition
Keeping the addition at +1 while only the multiplier grows

18 Sep 2025, 12:30, Reasoning Q.25 runs the same ×n + n rule as a wrong-term item: 6, 7, 16, 51, then 208 is due, so its printed 210 is keyed (a).

9 Sep 2024, 09:00, Reasoning Q.25 grows the multiplier but keeps adding 1: 1, 3, 10, 41, 206 (keyed d), 1237.

Related PYQs

No directly related past PYQ was found.

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