SSC CGL 2025 Tier-I · 14 September 2025, Shift 1 · General Intelligence and Reasoning · Question 8 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 11 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. From 2025 the candidate response sheet prints every question and option as a picture, so the text here is transcribed from those pictures for this shift and checked against them independently; where the layout carries meaning, the picture is shown as well. Each answer is the key SSC colour-marked on that sheet. SSC released a tentative key for challenge and later its final one, both only to candidates behind a login, and the sheet does not say which of the two it carries. The solutions are written by UnlockIAS.

What comes next: 3, 7, 16, 35, 74, ?

(a)153
(b)156
(c)151
(d)152

Answer

Why

Correct — A.
Rule: ×2, then add 1, 2, 3, 4, 5 in turn.

3 × 2 + 1 = 7
7 × 2 + 2 = 16
16 × 2 + 3 = 35
35 × 2 + 4 = 74

Next: 74 × 2 + 5 = 153 → option (a).

Why the others are wrong

(b)
156 — 156 needs a jump of 82 from 74. The gaps run 4, 9, 19, 39, each double the last plus 1, so the next gap is 79.
(c)
151 — 151 is 74 × 2 + 3, reusing an add already spent. The adds climb 1, 2, 3, 4, so the next one is +5.
(d)
152 — 152 is 74 × 2 + 4, repeating the last add. The adds climb by one each step, so after +4 comes +5, giving 153.

Concept

Two readings of this series agree. Multiply by 2 and add a number that grows by 1 each step. Or take the gaps, 4, 9, 19, 39, and notice each gap is double the last plus 1.

Either way the next gap is 79, and 74 + 79 = 153. Checking one reading against the other is a quick way to confirm a series rule before you commit.

The series opens 3, 7, like the ×2 + 1 series 3, 7, 15, 31. Here the third term is 16, not 15, and that is what tells you the add is growing.

Key facts

3, 7, 16, 35, 74 follows ×2 + 1, ×2 + 2, ×2 + 3, ×2 + 4.
The gaps 4, 9, 19, 39 each double the previous gap and add 1.
×2 + 1 at every step from 3 gives 3, 7, 15, 31, 63 instead.

Study next

Series built on ×2 plus a fixed number, such as 2, 5, 11, 23, 47Series whose gaps form a series of their own×n + k series in which k grows each step

Common traps

Assuming the fixed ×2 + 1 series from the opening 3, 7
Repeating the last add, +4, and choosing 152

17 Sep 2025, 16:00, Reasoning Q.24 starts the same way, 3, 7, 15, 31, 63, ?, but adds a fixed 1 each time and is keyed 127.

13 Sep 2024, 12:30, Reasoning Q.8 uses a fixed ×2 − 1: 9 17 33 65 129 ? is keyed 257.

Related PYQs

No directly related past PYQ was found.

Topic: Number Series — all 112 SSC CGL questions on it, every solved shift.