SSC CGL 2024 Tier-I · 19 September 2024, Shift 2 · General Intelligence and Reasoning · Question 16 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.

The second number in the given number-pairs is obtained by performing certain mathematical operation(s) on the first number. The same operation(s) is/are followed in all the number-pairs, except one. Find that odd number-pair. (NOTE: The relation should be found without breaking down the numbers into its constituent digits)

(a)1521 : 1600
(b)1764 : 1849
(c)1156 : 1225
(d)784 : 961

Answer

Why

Correct — D. Rule: each pair is a square and the very next square — n² : (n+1)².

1521 : 1600 = 39² : 40²
1764 : 1849 = 42² : 43²
1156 : 1225 = 34² : 35²
784 : 961 = 28² : 31²

Only the last pair skips: 28² is followed by 29² = 841, not 961, so option (d) is the odd number-pair.

Why the others are wrong

(a)
1521 : 1600 — 1521 = 39² and 1600 = 40², consecutive squares, so this pair obeys the rule and is not the odd one out.
(b)
1764 : 1849 — 1764 = 42² and 1849 = 43², again consecutive squares, so it sits with the majority.
(c)
1156 : 1225 — 1156 = 34² and 1225 = 35² — consecutive squares once more, so it is not the exception the stem wants.

Concept

An odd-one-out over number-pairs asks for the pair that does not share the majority's rule, so the first job is to find the rule three of the four obey.

The bracketed note blocks digit-level tricks, which points at whole-number operations: squares, cubes, multiples and the like.

Here all eight numbers are perfect squares, so the pair is (square, square) and the only question left is how far apart the two roots stand.

The answer is the pair that breaks the pattern, so the three options you reject are the ones that behave correctly — the opposite of the usual reading.

Key facts

The squares from 28 to 43 are worth knowing on sight: 784, 841, 900, 961, 1024, 1089, 1156, 1225, 1296, 1369, 1444, 1521, 1600, 1681, 1764, 1849.
The gap between consecutive squares n² and (n+1)² equals n + (n+1), so 1600 − 1521 = 79 = 39 + 40.
784 and 961 are 28² and 31², whose roots differ by 3 rather than 1.

Study next

Squares of 20 to 50 recognised on sightThe n + (n+1) gap as a quick test for consecutive squaresNumber-pair analogies where the operation acts on the whole number, as at Reasoning Q.18 of this shift

Common traps

Marking a pair that follows the rule, because the stem asks for the pair that does not.
Checking only that both numbers are perfect squares and stopping before comparing the roots.
Splitting the numbers into digits, which the stem's note forbids.

This stem carries the rider against breaking numbers into their digits, which tells you the operation acts on the whole number. Reasoning Q.13 of this shift runs the same odd-one-out frame over letter-clusters instead of numbers.

Related PYQs

No directly related past PYQ was found.