SSC CGL 2024 Tier-I · 19 September 2024, Shift 3 · General Intelligence and Reasoning · Question 15 of 99

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 four options are alike in a certain way and thus form a group. Which is the one that does NOT belong to that group? (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/subtracting/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)88 – 23 – 245
(b)56 – 31 – 205
(c)22 – 13 – 85
(d)18 – 12 – 72

Answer

Why

Correct — C. Rule: 2 × first + 3 × second = third.

88 and 23: 176 + 69 = 245 ✓
56 and 31: 112 + 93 = 205 ✓
18 and 12: 36 + 36 = 72 ✓

Option (c) is the one that breaks it. 2 × 22 + 3 × 13 = 44 + 39 = 83, but the triple prints 85.

A two-unit gap is small enough to miss by eye, which is exactly why this item rewards recomputing rather than glancing.

Why the others are wrong

(a)
88 – 23 – 245 — 2 × 88 + 3 × 23 = 245, the printed third number. It obeys the shared rule, so it belongs to the group and cannot be the odd one.
(b)
56 – 31 – 205 — 2 × 56 + 3 × 31 = 205, matching what is printed. It sits inside the group with (a) and (d).
(d)
18 – 12 – 72 — 2 × 18 + 3 × 12 = 72, exactly the printed value. The smallest numbers here still satisfy the same weighted sum.

Concept

An odd-one-out on number groups inverts the usual analogy task. You are not looking for a rule that fits everything; you need one that fits exactly three of four and fails the fourth.

So look for the relation shared by the majority, not the one that explains the triple you already suspect. Any rule you can only make work on one option is noise.

Weighted sums, ax + by = c, are worth testing when the third number is much larger than the first two but is not a clean product of them.

The break is deliberately narrow. The rule predicts 83 and the paper prints 85, so a candidate who estimates rather than multiplies will pass straight over it.

Key facts

Three of the four triples satisfy 2 × first + 3 × second = third.
Option (c) yields 83 by that rule while printing 85.
The other three match their printed third numbers exactly, at 245, 205 and 72.
The NOTE bars digit-splitting, so 22 is twenty-two rather than a 2 and a 2.

Study next

Weighted sums ax + by = c in number-group itemsOdd-one-out logic, where the rule must fit three of four and fail oneDeciding between sum, product and weighted-sum shapes from the size of the third number

Common traps

Hunting for a rule that fits all four, which cannot exist in an odd-one-out
Testing simple differences such as 88 − 23 = 65, which leads nowhere on the other triples
Accepting option (c) because 83 and 85 look close

Odd-one-out is also set on letter-clusters at Reasoning Q.3, 19 Sep 2024, 16:00. The material changes but the method does not: find the relation three of them share, then name the one left outside it.

Related PYQs

No directly related past PYQ was found.