SSC CGL 2025 Tier-I · 17 September 2025, Shift 3 · General Intelligence and Reasoning · Question 9 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.

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.

Complete the series: 1331, 10648, 35937, 85184, ?

(a)15478
(b)189384
(c)166375
(d)136789

Answer

Why

Correct — C.
Rule: each term is the cube of the next multiple of 11.

1331 = 11³ and 10648 = 22³
35937 = 33³ and 85184 = 44³

Next term: 55³
55² = 3025, and 3025 × 55 = 166375 → option (c).

Why the others are wrong

(a)
15478 — 15478 is smaller than 85184, yet the series keeps rising. It is not a cube either: it lies between 24³ = 13824 and 25³ = 15625.
(b)
189384 — 189384 is not a cube: 57³ = 185193 and 58³ = 195112 sit either side of it. The next base is 55, not 57 or 58.
(d)
136789 — 136789 ends in 9, but 55³ must end in 5, as the cube of any number ending in 5 does. It lies between 51³ and 52³.

Concept

When the terms of a series grow this fast, test them for powers. The first term, 1331, is 11³, and a ratio check confirms the pattern: 10648 ÷ 1331 = 8 = 2³.

So the terms are 1331 × 1³, 1331 × 2³, 1331 × 3³, 1331 × 4³, and the next is 1331 × 5³ = 1331 × 125 = 166375.

A last-digit check settles it without multiplying. The next base is 55, and a number ending in 5 cubes to a number ending in 5. 166375 is the lone option that does.

Key facts

11³ = 1331, 22³ = 10648, 33³ = 35937, 44³ = 85184, 55³ = 166375.
(11n)³ = 1331 × n³, so the terms are 1331 times 1, 8, 27, 64 and 125.
A number ending in 5 has a cube ending in 5.

Study next

Series of squares and cubes with a constant added or subtractedCube-root analogies, such as 64 : 4 :: 729 : 9Unit digits of squares and cubes

Common traps

Hunting for a common difference in terms that grow by multiplication
Not recognising 1331 as 11³, which unlocks every other term

Cube recognition is also tested as an analogy: 11 Sep 2024, 09:00, Reasoning Q.21 maps 8 to 512 and 12 to 1728, so 15 maps to 3375.

24 Sep 2024, 16:00, Reasoning Q.3 runs it backwards, 64 to 4 and 216 to 6, so 729 maps to 9.

Related PYQs

No directly related past PYQ was found.

Topic: Number Series — all 112 SSC CGL questions on it, every solved shift.