SSC CGL 2024 Tier-I · 12 September 2024, Shift 2 · General Intelligence and Reasoning · Question 12 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 6 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.

Three of the following numbers are alike in a certain way and one is different. Pick the odd one out. (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)12 – 7 – 209
(b)19 – 11 – 330
(c)23 – 8 – 343
(d)15 – 9 – 264

Answer

Why

Correct — C. Rule: third number = 11 × (first + second).

12 – 7 – 209: 12 + 7 = 19, and 19 × 11 = 209
19 – 11 – 330: 19 + 11 = 30, and 30 × 11 = 330
15 – 9 – 264: 15 + 9 = 24, and 24 × 11 = 264

23 – 8 – 343: 23 + 8 = 31, and 31 × 11 = 341, not 343.

So the set that breaks the rule is 23 – 8 – 343 — option (c).

Why the others are wrong

(a)
12 – 7 – 209 — 12 + 7 = 19 and 19 × 11 = 209, so this set obeys the rule and belongs to the group.
(b)
19 – 11 – 330 — 19 + 11 = 30 and 30 × 11 = 330 — an exact fit, so this is not the outsider.
(d)
15 – 9 – 264 — 15 + 9 = 24 and 24 × 11 = 264, again a clean fit, which keeps it inside the group.

Concept

An odd-one-out on number triples means finding the single operation that ties the first two numbers to the third, then finding the set that misses it.

Start with the cheapest tests: sum, difference, product, then a shared factor. 209, 330 and 264 are all multiples of 11, and dividing each by 11 gives 19, 30 and 24 — exactly the sums of the first two numbers.

343 is 7 × 7 × 7 and carries no factor of 11, which spots it before any of the arithmetic above is done.

The printed note bars digit-splitting, so 209 stays 209 and is never read as 2, 0 and 9. That closes off the digit-sum readings this format otherwise invites.

Key facts

209 = 11 × 19, 330 = 11 × 30 and 264 = 11 × 24.
In each of those sets the multiplier of 11 is the sum of the first two numbers.
23 + 8 = 31 and 31 × 11 = 341, whereas the set prints 343.
343 = 7 × 7 × 7, which has no factor of 11.

Study next

Divisibility tests for 11, 7 and 13Odd-one-out sets built on a square or a cube of one memberTwo-number odd-one-out pairs, as at 9 Sep 2024, 16:00, Reasoning Q.4

Common traps

Testing only the first two sets and fixing the rule from them alone
Seeing that 343 is a perfect cube and treating that as the rule rather than the exception
Breaking the three-digit number into digits, which the note forbids

Triple-number odd-one-out sets are asked at 13 Sep 2024, 09:00, Reasoning Q.16 (31 – 5 – 160, 13 – 8 – 109, 21 – 4 – 89, 27 – 9 – 243) and at 23 Sep 2024, 09:00, Reasoning Q.6 (18 – 11 – 63, 12 – 8 – 36, 21 – 14 – 72, 15 – 3 – 108).

Related PYQs

No directly related past PYQ was found.