SSC CGL 2025 Tier-I · 22 September 2025, Shift 1 · Quantitative Aptitude · Question 10 of 98

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 13 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.

The difference between 20% of a number and 10% of the same number is 120. What is the number?

(a)1000
(b)1100
(c)1200
(d)1400

Answer

Why

Correct — C. Both percentages are taken of the same number N, so subtract the percentages first.

Subtract the rates: 20% of N − 10% of N = 10% of N
Set it equal to the gap: 10% of N = 120
Multiply by 10 to reach 100%: N = 120 × 10 = 1200 → option (c)

Check: 20% of 1200 = 240, 10% of 1200 = 120, and 240 − 120 = 120.

Why the others are wrong

(a)
1000 — 10% of 1000 is 100, not 120. 20% of 1000 = 200 and 10% of 1000 = 100, so the gap is 100, short of the 120 in the stem.
(b)
1100 — 10% of 1100 is 110. The gap between 220 and 110 is 110, still 10 short of 120, so 1100 is too small.
(d)
1400 — 10% of 1400 is 140. 280 − 140 = 140, which overshoots the stated difference of 120 by 20.

Concept

When two percentages are taken of the same number, their difference is itself a percentage of that number: a% of N − b% of N = (a − b)% of N.

So the stem reduces to one fact, 10% of N = 120. Scaling 10% up to 100% (multiply by 10) recovers N.

Subtracting the rates first turns the question into a single division.

Every option can be tested in seconds: divide it by 10 and compare with 120. 1200 is the option that gives exactly 120.

Key facts

a% of N − b% of N = (a − b)% of N, because both terms share the base N.
10% of a number is the number divided by 10: 10% of 1200 = 120.
If p% of N = k, then N = k × 100 ⁄ p: here 120 × 100 ⁄ 10 = 1200.

Study next

Stems of the form 'x% of a number is k more than y% of it'Finding the whole from a part: N = k × 100 ⁄ pComparing percentages taken of two different bases

Common traps

Reading 'difference' as a sum: 30% of N = 120 gives N = 400, which is not an option.
Treating 120 as 20% of N and answering 600, which ignores the 10% being subtracted.

The stem gives the gap between two percentages of one number and asks for the number. The same subtraction solves 14 Sep 2025, 12:30, Quant Q.4, where 45% of a number is 0.9 more than 30% of it, so 15% of the number is 0.9 and the number is 6.

Related PYQs

No directly related past PYQ was found.

Topic: Percentage — all 82 SSC CGL questions on it, every solved shift.