SSC CGL 2024 Tier-I · 10 September 2024, Shift 3 · General Intelligence and Reasoning · Question 1 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 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)81 – 118 – 91
(b)52 – 68 – 51
(c)21 – 38 – 31
(d)99 – 104 – 71

Answer

Why

Correct — B. One relation ties all three numbers of a set together.

Rule: second - third = first divided by 3.

(a) 81 / 3 = 27, and 118 - 91 = 27 — fits.
(c) 21 / 3 = 7, and 38 - 31 = 7 — fits.
(d) 99 / 3 = 33, and 104 - 71 = 33 — fits.

(b) 52 is not divisible by 3 at all, and 68 - 51 = 17.

The relation breaks only there, so option (b) is the set that does not belong.

Why the others are wrong

(a)
81 – 118 – 91 — 81 / 3 = 27 and 118 - 91 = 27, an exact fit, so this set sits inside the group. The odd one out is the set that fails the relation, not one that passes it.
(c)
21 – 38 – 31 — 21 / 3 = 7 and 38 - 31 = 7. The numbers are the smallest of the four sets, but size is not what these items group on.
(d)
99 – 104 – 71 — 99 / 3 = 33 and 104 - 71 = 33. It fits like the others, and its larger numbers are there to make it look different when it is not.

Concept

SSC's odd-one-out number sets almost never group on size, and rarely on a difference you can see at a glance. They group on a relation that binds all three numbers.

So look for a link between the outer numbers and the middle one, not only at consecutive gaps. Here the first number divided by 3 reproduces the gap between the second and the third.

The NOTE in the stem is a real constraint. You may add, subtract, multiply or divide the whole numbers, but you may not split 81 into 8 and 1 and work on the digits.

Consecutive differences alone separate nothing here.

They run 37 and -27 in (a), 17 and -7 in (c), 5 and -33 in (d), 16 and -17 in (b) — four unrelated-looking pairs until you divide the first number by 3.

Key facts

In sets (a), (c) and (d) the relation is second - third = first / 3.
The first number is a multiple of 3 in every set that fits: 81, 21 and 99.
52 is not divisible by 3, which is what makes option (b) the odd set.

Study next

Odd-one-out number sets built on first / n = second - thirdTwo-number analogy sets of the form second = 2 x first - a constantDivisibility tests for 3 and 9 applied to the whole number

Common traps

Checking only consecutive differences, which gives 37, 17, 5 and 16 and settles nothing.
Splitting 81 into 8 and 1, which the stem's NOTE forbids.
Choosing (d) because 99 and 104 look unlike the smaller sets.

SSC builds these sets so that one multiplication or division links the three numbers, and the whole-number NOTE that comes with them tells you to operate on the numbers as printed, never on their digits.

The same rule family also drives the number-set analogies at 10 Sep 2024, 16:00, Reasoning Q.5 and Reasoning Q.7.

Related PYQs

No directly related past PYQ was found.