SSC CGL 2024 Tier-I · 23 September 2024, Shift 2 · General Intelligence and Reasoning · Question 21 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.

Select the set in which the numbers are related in the same way as are the numbers of the following set. (84, 63, 42) (79, 47, 64) (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)(71, 53, 36)
(b)(64, 51, 52)
(c)(67, 48, 57)
(d)(75, 33, 48)

Answer

Why

Correct — A. The third number is fixed by the gap between the first two.

Rule: third = 2 × (first − second).

(84, 63, 42): 84 − 63 = 21, and 2 × 21 = 42
(79, 47, 64): 79 − 47 = 32, and 2 × 32 = 64

Testing option (a): 71 − 53 = 18, and 2 × 18 = 36

So (71, 53, 36) obeys the same relation.

Why the others are wrong

(b)
(64, 51, 52) — 64 − 51 = 13, so the third number should be 26. The printed 52 is 4 × 13, twice too large.
(c)
(67, 48, 57) — 67 − 48 = 19, so the third number should be 38. The printed 57 is 3 × 19.
(d)
(75, 33, 48) — 75 − 33 = 42, so the third number should be 84. The printed 48 is not even a multiple of 42.

Concept

The second worked set is what makes this question solvable. (84, 63, 42) falls by 21 twice and looks like a plain arithmetic progression.

But (79, 47, 64) does not fall at all — its third number is larger than its second — so a progression rule is dead before you reach the options.

What survives both sets is a relation among the three numbers rather than a sequence: double the gap between the first two to get the third. When two worked sets disagree about the shape, the rule is a relation.

The bracketed NOTE bars digit operations, so do not look for a rule joining the 8 and the 4 of 84.

Key facts

Set 1: 84 − 63 = 21 and 2 × 21 = 42.
Set 2: 79 − 47 = 32 and 2 × 32 = 64.
The three numbers need not decrease — in (79, 47, 64) the third exceeds the second.

Study next

Set analogies where the third number is the sum or the product of the first twoSets held together by a common divisor rather than by a differenceTwo-number pair analogies, which carry the same NOTE about whole numbers

Common traps

Reading (84, 63, 42) as an arithmetic progression and never testing the second set
Taking the third number as the gap itself rather than twice the gap
Testing an option against one worked set only, where a near-rule can survive

Three-number set analogies with two worked sets recur across the 2024 shifts — also asked 10 Sep 2024, 09:00, Reasoning Q.9 (sets (79, 58, 62) and (54, 33, 37)) and 9 Sep 2024, 16:00, Reasoning Q.23 (sets (34, 47, 62) and (119, 142, 167)).

Related PYQs

No directly related past PYQ was found.