SSC CGL 2024 Tier-I · 12 September 2024, Shift 3 · 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 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. (34, 17, 27) (42, 21, 31) (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)(38, 16, 36)
(b)(54, 27, 37)
(c)(46, 23, 35)
(d)(64, 34, 54)

Answer

Why

Correct — B. Read both model sets as a two-step chain.

(34, 17, 27): 34 ÷ 2 = 17, then 17 + 10 = 27 ✓
(42, 21, 31): 42 ÷ 2 = 21, then 21 + 10 = 31 ✓

Rule: second = first ÷ 2, then third = second + 10.

Apply it to option (b): 54 ÷ 2 = 27 ✓, then 27 + 10 = 37 ✓. Both steps hold, so option (b) is the matching set.

Why the others are wrong

(a)
(38, 16, 36) — (38, 16, 36) fails at step one — 38 ÷ 2 = 19, not 16. Once the halving breaks there is no reason to look at the third number at all.
(c)
(46, 23, 35) — (46, 23, 35) passes the halving, since 46 ÷ 2 = 23, and then fails step two: 23 + 10 = 33, not 35. That near-miss is what makes it the trap.
(d)
(64, 34, 54) — (64, 34, 54) fails immediately — 64 ÷ 2 = 32, not 34. The gap of 20 between 34 and 54 is a different rule from the +10 both model sets use.

Concept

When a set holds three numbers, look for a chain — first to second, then second to third — rather than one formula tying all three together. Chains are quicker to test and much harder to fake.

Check both steps on both model sets before opening the options. A rule that fits one set is a coincidence.

Then test each option step by step and stop at the first failure. Most wrong options here break on step one, so elimination is fast.

The chain can also be written in one line as third = (first + 20) ÷ 2, which is the same rule rearranged: (34 + 20) ÷ 2 = 27 and (54 + 20) ÷ 2 = 37. Either form picks out the same set.

Key facts

The chain is second = first ÷ 2, then third = second + 10.
Both printed sets obey it: 34 → 17 → 27 and 42 → 21 → 31.
Option (b) gives 54 → 27 → 37, satisfying both steps.

Study next

Three-number set analogies solved as two chained stepsSets whose rule mixes a division with an additionTesting a candidate rule against every worked example before using it

Common traps

Checking the halving, seeing it work and assuming the rest follows, which is how (46, 23, 35) picks up answers.
Deriving the rule from one model set only.

The same select-the-set wording appears at 12 Sep 2024, 16:00, Reasoning Q.19, there with a double-the-product rule. SSC's whole-number NOTE is printed on both.

Related PYQs

No directly related past PYQ was found.