SSC CGL 2025 Tier-I · 20 September 2025, Shift 1 · General Intelligence and Reasoning · Question 22 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 should come at the place of question mark? : 8, 27, 64, 125, ?, 343

(a)200
(b)216
(c)243
(d)250

Answer

Why

Correct — B.
Rule: consecutive cubes, from 2³ to 7³.

8 = 2³, 27 = 3³, 64 = 4³, 125 = 5³
? = 6³ = 6 × 6 × 6 = 216
343 = 7³ closes the run → option (b)

Why the others are wrong

(a)
200 — 200 is not a cube. It falls between 5³ = 125 and 6³ = 216, and the term after 125 must be the next cube.
(c)
243 — 243 is 3⁵, a power of 3 but not the cube of a whole number. The term between 5³ and 7³ is 6³ = 216.
(d)
250 — 250 is 2 × 125, doubling the term before it. The terms are cubes, not doublings: 64 is not 2 × 27, and 125 is not 2 × 64.

Concept

When the terms of a series grow fast and unevenly, test powers before differences. 8, 27 and 64 are the cubes of 2, 3 and 4, and the last term, 343 = 7³, confirms the run.

Differences also work, more slowly. The gaps 19, 37, 61, 91, 127 grow by 18, 24, 30, 36, and those steps rise by a constant 6, which is how cubes behave.

The printed 343 after the gap is a free check: 216 = 6³ leads straight to 7³ = 343.

Key facts

Cubes 1 to 10: 1, 8, 27, 64, 125, 216, 343, 512, 729, 1000.
6³ = 216 and 7³ = 343.
243 = 3⁵ is a power of 3 but not a perfect cube.

Study next

Series of squares or cubes with one term replacedCube-based series with a twist, such as n³ + 1Third-difference checks in number series

Common traps

Picking 243 because it looks like a familiar power. It is 3⁵, not a cube.
Doubling 125 to 250 without checking what the earlier terms share.

Cubes also decide 14 Sep 2025, 16:00, Reasoning Q.17, where the odd term in 1, 8, 27, 64, 121, 216 is 121, standing where 5³ = 125 belongs.

Related PYQs

No directly related past PYQ was found.

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