SSC CGL 2024 Tier-I · 18 September 2024, Shift 2 · General Intelligence and Reasoning · Question 9 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 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.

Two sets of numbers are given below. In each set of numbers, certain mathematical operation(s) on the first number result(s) in the second number. Similarly, certain mathematical operation(s) on the second number result(s) in the third number and so on. Which of the given options follows the same set of operations as in the given sets? (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.) 7 – 14 – 28 – 38; 4 – 8 – 16 – 26

(a)6 – 12 – 24 – 36
(b)13 – 26 – 52 – 62
(c)8 – 16 – 32 – 40
(d)15 – 25 – 50 – 60

Answer

Why

Correct — B. Rule: ×2, then ×2, then +10 across the four terms.

7 to 14 is ×2, 14 to 28 is ×2, 28 to 38 is +10.
4 to 8 is ×2, 8 to 16 is ×2, 16 to 26 is +10.

Now test option (b): 13 to 26 is ×2, 26 to 52 is ×2, and 52 + 10 = 62.
All three steps match, so it is option (b).

Why the others are wrong

(a)
6 – 12 – 24 – 36 — 6 to 12 to 24 doubles correctly, but the last step 24 to 36 is +12, not +10.
(c)
8 – 16 – 32 – 40 — 8 to 16 to 32 doubles correctly, then 32 to 40 is +8, not +10.
(d)
15 – 25 – 50 – 60 — 15 to 25 fails at the first step. That is +10, and the first operation in both given chains is a doubling.

Concept

Chain items hand you two worked examples precisely so that a rule fitting only one of them can be thrown out.

Write the operation above each arrow rather than the difference. 7 to 14 is not merely +7, it is ×2, and the second chain, 4 to 8, is what proves it.

Then read the final arrow on its own. Both given chains end with a constant +10, and that step is where the question is decided, because three of the four options double correctly.

The bracketed note bans digit-level work, so 38 is not to be read as a 3 and an 8. Every operation is arithmetic on the whole number.

Key facts

Both given chains run ×2, then ×2, then +10.
The worked sets are 7 - 14 - 28 - 38 and 4 - 8 - 16 - 26.
13 doubles to 26, doubles again to 52, and 52 + 10 = 62.

Study next

Number chains mixing multiplication with a constant additionSeries where the operation alternates between two rulesAnalogy pairs written as A : B :: C : ?

Common traps

Fitting a rule to the first chain alone when the second chain is what pins it.
Assuming the last step is another doubling because the first two were.
Treating a difference as the operation when a ratio fits both terms equally well.

The same two-set stem, bracketed note included, is asked on 12 Sep 2024, 12:30, Reasoning Q.2 and on 13 Sep 2024, 16:00, Reasoning Q.16.

Related PYQs

No directly related past PYQ was found.

Two sets of numbers are given below. In each set of numbers, certain mathematical operation(s) on the first number result(s) in the second number. Similarly, certain mathematical operation(s) on the second number result(s) in the third number and so on. Which of the given options follows the same set of operations as in the given sets? (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.) 7 – 14 – 28 – 38; 4 – 8 – 16 – 26

(a)6 – 12 – 24 – 36
(b)13 – 26 – 52 – 62
(c)8 – 16 – 32 – 40
(d)15 – 25 – 50 – 60