SSC CGL 2024 Tier-I · 25 September 2024, Shift 1 · General Intelligence and Reasoning · Question 24 of 100

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 10 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

The same operation(s) are followed in all the given number pairs except one. Find that odd number pair. (NOTE : Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding /deleting /multiplying etc., to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

(a)22 : 45
(b)7 : 15
(c)11 : 121
(d)5 : 11

Answer

Why

Correct — C. Fix the rule on the smallest pair, then carry it across the rest.

5 : 11 gives 5 × 2 + 1 = 11
7 : 15 gives 7 × 2 + 1 = 15
22 : 45 gives 22 × 2 + 1 = 45

Rule: the second number is the first doubled, plus one.

11 : 121 breaks it, because 11 × 2 + 1 is 23, not 121. That pair squares instead, so option (c) is the odd one.

Why the others are wrong

(a)
22 : 45 — 22 doubles to 44 and one more is 45, so this pair obeys the shared rule and cannot be the odd one out.
(b)
7 : 15 — 7 doubles to 14 and one more is 15. Same rule, so this pair sits with the majority.
(d)
5 : 11 — 5 doubles to 10 and one more is 11. It is the pair that makes the rule easiest to spot, not the exception to it.

Concept

An odd-pair item is decided by majority. Find the rule three of the four pairs share, then name the fourth.

Start with the smallest numbers, because a small pair admits few rules. 5 : 11 could be double-and-add-one, or add six, or one or two others. Testing 7 : 15 kills add-six and confirms double-and-add-one.

With the rule fixed the rest is arithmetic: 22 : 45 fits, and 11 : 121 does not, because 121 is 11 squared — a different relation entirely.

11 : 121 is the trap precisely because it looks meaningful. A pair can obey a perfectly good rule of its own and still be the odd one, since the question asks which pair leaves the group, not which pair is unstructured.

Key facts

Three of the four pairs follow second = first doubled plus one.
5 × 2 + 1 = 11, 7 × 2 + 1 = 15 and 22 × 2 + 1 = 45.
11 × 2 + 1 = 23, but the pair prints 121, which is 11 squared.

Study next

Odd-one-out number pairs, fixing the rule from the smallest pair firstTelling a linear relation apart from a power relation at a glanceThe whole-number NOTE and the digit-based rules it excludes

Common traps

Spotting 121 as 11 squared and adopting that as the shared rule
Testing the candidate rule on one pair only and stopping there
Reading the question as which pair has no pattern rather than which pair leaves the group

SSC reuses the frame with different arithmetic. At 25 Sep 2024, 16:00, Reasoning Q.24 the pairs are 11 : 143, 13 : 169, 12 : 152 and 15 : 195 on a multiply-by-13 rule, and at 19 Sep 2024, 09:00, Reasoning Q.23 they are 24 : 4, 49 : 8, 19 : 3 and 55 : 9.

Related PYQs

No directly related past PYQ was found.