SSC CGL 2025 Tier-I · 21 September 2025, Shift 3 · General Intelligence and Reasoning · Question 6 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.

Find the WRONG number in the given series. 5040, 720, 120, 24, 4, 2

(a)720
(b)24
(c)4
(d)130

Answer

Why

Correct — C.
Rule: divide by 7, 6, 5, 4, 3 in turn (the correct terms are 7!, 6!, 5!, 4!, 3!, 2!).

5040 ÷ 7 = 720, fits.
720 ÷ 6 = 120, fits.
120 ÷ 5 = 24, fits.
24 ÷ 4 = 6, but the series prints 4.

Then 6 ÷ 3 = 2 fits the last term, so 4 is the wrong number → option (c).

Why the others are wrong

(a)
720 — 720 is 6! = 6 × 5 × 4 × 3 × 2 × 1, and 5040 ÷ 7 = 720 exactly. It sits on the rule.
(b)
24 — 24 is 4! and equals 120 ÷ 5, so it fits. The break comes one step later, where 24 ÷ 4 should give 6.
(d)
130 — 130 does not appear in the series as printed. The nearby term is 120, which is 5! and equals 720 ÷ 6, so it is correct too.

Concept

A wrong-term item hides one bad number in a series that is otherwise exact. Find the rule from the terms that agree, then check every term against it.

Here each term is the one before divided by a number that falls by one: ÷7, ÷6, ÷5, ÷4, ÷3. Read from the right, the terms are factorials: 2! = 2, 3! = 6, 4! = 24, 5! = 120, 6! = 720, 7! = 5040. The series needs 6 where it prints 4.

Option (d), 130, is printed on the response sheet but is not a term of the series. It cannot be the wrong term, so the real choice is among 720, 24 and 4.

Key facts

n! (n factorial) is the product 1 × 2 × … × n, so 5! = 120.
3! = 6, 4! = 24, 5! = 120, 6! = 720 and 7! = 5040.
Dividing n! by n gives (n − 1)!, which is why each step here divides by one less.

Study next

Series built by multiplying by 1, 2, 3, 4 … (rising factorials)Wrong-term items built on squares or cubesSeries with alternating × and ÷ steps

Common traps

Checking only the differences (4320, 600, 96 …), which show no clean pattern in a factorial series
Blaming the last term, 2: once 4 is corrected to 6, 6 ÷ 3 = 2 fits

18 Sep 2025, 12:30, Reasoning Q.6 is a wrong-term item too: 5, 10, 15, 26, 37, 50 follows n² + 1, so 15 is keyed where 17 belongs.

19 Sep 2025, 09:00, Reasoning Q.6 steps down by 90, 80, 70, 60, 50, so 94 is keyed where 96 belongs.

Related PYQs

No directly related past PYQ was found.

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