2, 4, 8. **2, 4, 8** is 2, 2², 2³: each term is the one before multiplied by 2. It follows the rule.

3, 9, 27. **3, 9, 27** is 3, 3², 3³, multiplying by 3 at each step. It follows the rule.

5, 25, 125. **5, 25, 125** is 5, 5², 5³, multiplying by 5 at each step. It follows the rule.

SSC CGL 2025 Tier-I · 13 September 2025, Shift 2 · General Intelligence and Reasoning · Question 17 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.

Choose the odd one:

(a)2, 4, 8
(b)3, 9, 27
(c)5, 25, 125
(d)4, 16, 36

Answer

Why

Correct — D.
Rule: n, n², n³ (each term is the one before multiplied by the first).

2, 4, 8 = 2, 2², 2³
3, 9, 27 = 3, 3², 3³
5, 25, 125 = 5, 5², 5³

4, 16 fits 4, 4², but 4³ = 64, not 36. This group breaks the rule → option (d).

Why the others are wrong

(a)
2, 4, 8 — 2, 4, 8 is 2, 2², 2³: each term is the one before multiplied by 2. It follows the rule.
(b)
3, 9, 27 — 3, 9, 27 is 3, 3², 3³, multiplying by 3 at each step. It follows the rule.
(c)
5, 25, 125 — 5, 25, 125 is 5, 5², 5³, multiplying by 5 at each step. It follows the rule.

Concept

An odd-one-out among number groups asks for the property that three groups share and one breaks. Test the simplest relation first: how each term follows from the one before.

Here each regular group is a number followed by its square and cube, so the multiplier equals the first term. In 4, 16, 36 the step from 16 to 36 is ×2.25, not ×4.

4, 16, 36 has a pattern of its own: 2², 4², 6², the squares of even numbers. It is still the odd group, because it does not share n, n², n³ with the rest.

Key facts

Cubes to know: 2³ = 8, 3³ = 27, 4³ = 64, 5³ = 125.
Squares of even numbers: 2² = 4, 4² = 16, 6² = 36.
In n, n², n³ the ratio between neighbouring terms is n.

Study next

Odd-one-out on number triples built from squares and cubesNumber series with a constant ratio (geometric progressions)Prime-number triples in odd-one-out items

Common traps

Seeing 4 and 16 fit 4, 4² and accepting the group without checking the third term
Spotting 2², 4², 6² in 4, 16, 36 and then hunting for a squares pattern in the other groups

12 Sep 2025, 09:00, Reasoning Q.18 also sets three-number groups as an odd-one-out, but its rule is primality: 4, 6, 8 is keyed as the group with no prime.

Related PYQs

No directly related past PYQ was found.

Topic: Semantic Classification — all 59 SSC CGL questions on it, every solved shift.