SSC CGL 2024 Tier-I · 12 September 2024, Shift 2 · General Intelligence and Reasoning · Question 5 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.

Select the set in which the numbers are related in the same way as are the numbers of the following set. (11, 16.5, 22) (14.5, 20, 25.5) (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)(14, 18.5, 23.5)
(b)(21.5, 25, 31.5)
(c)(24.5, 30, 36.5)
(d)(18, 23.5, 29)

Answer

Why

Correct — D. Rule: an arithmetic progression with a common difference of 5.5.

(11, 16.5, 22): 11 + 5.5 = 16.5, then 16.5 + 5.5 = 22
(14.5, 20, 25.5): 14.5 + 5.5 = 20, then 20 + 5.5 = 25.5

Apply the same step to option (d):
18 + 5.5 = 23.5, then 23.5 + 5.5 = 29.

Why the others are wrong

(a)
(14, 18.5, 23.5) — 18.5 − 14 = 4.5 and 23.5 − 18.5 = 5. Neither gap is 5.5, and the two gaps are not even equal to each other.
(b)
(21.5, 25, 31.5) — 25 − 21.5 = 3.5 while 31.5 − 25 = 6.5, so this is not an arithmetic progression at all.
(c)
(24.5, 30, 36.5) — The first step is right — 30 − 24.5 = 5.5 — but 36.5 − 30 = 6.5, so the second step breaks the run.

Concept

Test three things in order on a set like this: a constant difference, a constant ratio, then a fixed formula tying the first number to the rest.

Take the differences first, because they are the cheapest test. Both sample sets step up by 5.5 twice, which settles the rule before any multiplication is tried.

The decimal is the whole difficulty. A step of 5.5 looks wrong until you see it twice in a row, and a candidate who rounds it to 5 or 6 will find no option that fits.

Checking one step is not enough. Option (c) matches the first difference exactly and fails on the second, so both gaps have to be tested before an option is accepted.

Key facts

Both sample sets step up by 5.5: 11, 16.5, 22 and 14.5, 20, 25.5.
Option (d) is 18, 23.5, 29 — two steps of 5.5.
Three numbers form an arithmetic progression when the middle one is the average of the outer two, and (18 + 29) divided by 2 is 23.5.

Study next

Number sets linked by a formula such as first times second plus third, rather than by a differenceArithmetic progressions with fractional common differencesNumber pairs where the second is derived from the first, as at 11 Sep 2024, 09:00, Reasoning Q.2

Common traps

Checking only an option's first gap and stopping, which lets option (c) through
Rounding the 5.5 step to 5 or to 6 and then finding no option that matches
Splitting 16.5 into 16 and 5, which the question's note forbids

Three-number sets with a constant difference are asked at 11 Sep 2024, 16:00, Reasoning Q.9, where (66, 57, 48) and (94, 85, 76) both step down by 9 and the key is (81, 72, 63).

Related PYQs

No directly related past PYQ was found.