SSC CGL 2024 Tier-I · 9 September 2024, Shift 1 · General Intelligence and Reasoning · Question 25 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.

Which of the following numbers will replace the question mark (?) in the given series? 1, 3, 10, 41, ?, 1237

(a)202
(b)210
(c)200
(d)206

Answer

Why

Correct — D. The differences 2, 7, 31 grow far too fast for an additive rule, so try multiply-and-add.

Rule: multiply by 2 and add 1, then by 3 and add 1, then by 4, 5, 6 and add 1 each time.

1 times 2 + 1 = 3
3 times 3 + 1 = 10
10 times 4 + 1 = 41
41 times 5 + 1 = 206

206 times 6 + 1 = 1237

The last line reproduces the term the question already prints, so 206 is confirmed rather than guessed — option (d).

Why the others are wrong

(a)
202 — 202 is 41 times 5 minus 3, which breaks the plus-one. It also fails the built-in check, since 202 times 6 plus 1 is 1213 and not the printed 1237.
(b)
210 — 210 adds 5 instead of 1 after multiplying by five. Carried one step further, 210 times 6 plus 1 is 1261, overshooting the printed final term.
(c)
200 — 200 falls short of 41 times 5 before anything is added at all, and 200 times 6 plus 1 is 1201, missing the printed 1237 by 36.

Concept

When a series climbs faster than an arithmetic progression but slower than a fixed geometric one, the usual shape is a multiplier that changes term by term.

Test it by dividing each term by the one before: 3 over 1 is 3, 10 over 3 is a little over 3, 41 over 10 is about 4. A multiplier drifting upward by one is the signature.

Once the multiplier is identified, the small constant is found from the first step, and the rule can be written as: each term is the previous term times its own multiplier, plus 1.

The question prints a term after the blank. That is not decoration. It lets you verify the candidate before marking, which is rare enough in a series item to be worth using every time it appears.

Key facts

The completed series is 1, 3, 10, 41, 206, 1237.
Each term equals the previous term multiplied by its position count and increased by 1, with the multiplier starting at 2.
The printed final term acts as a check: any candidate for the blank must give 1237 when multiplied by 6 and increased by 1.

Study next

Series where the multiplier stays fixed but the added constant changes, such as times 2 plus 1, times 2 plus 2Series generated by n squared plus n or n cubed minus n rather than from the previous termUsing a term printed after the blank to verify a candidate before marking it

Common traps

Hunting for a difference pattern, since 2, 7 and 31 lead nowhere
Fixing the multiplier at a single value, which gives 205 from 41 and misses the plus-one
Ignoring the printed final term, which is placed there precisely to settle the blank

SSC often prints one term beyond the blank in multiply-and-add series. Solve forward to the blank, then run one more step to the printed term.

If that step does not land exactly on the printed value, the rule is wrong and the answer you were about to mark is wrong with it.

Related PYQs

No directly related past PYQ was found.