SSC CGL 2025 Tier-I · 19 September 2025, Shift 1 · Quantitative Aptitude · Question 2 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.

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If 25% of A = 20% of B = 10% of C, find A : B : C.

(a)4 : 5 : 10
(b)10 : 5 : 4
(c)5 : 4 : 10
(d)2 : 3 : 5

Answer

Why

Correct — A.
Write the percentages as fractions: 25% = 1⁄4, 20% = 1⁄5, 10% = 1⁄10
Set each part equal to k: A⁄4 = B⁄5 = C⁄10 = k

Solve for each amount: A = 4k, B = 5k, C = 10k
Drop k: A : B : C = 4 : 5 : 10 → option (a)

Check: 25% of 4 = 1, 20% of 5 = 1, 10% of 10 = 1.

Why the others are wrong

(b)
10 : 5 : 4 — 10 : 5 : 4 lists the right numbers in reverse, which is C : B : A. Test it: 25% of 10 = 2.5 but 20% of 5 = 1, so the parts are not equal.
(c)
5 : 4 : 10 — 5 : 4 : 10 swaps A and B. 25% of 5 = 1.25 while 20% of 4 = 0.8, so the first two parts already disagree.
(d)
2 : 3 : 5 — 2 : 3 : 5 gives parts of 0.5, 0.6 and 0.5 (25% of 2, 20% of 3, 10% of 5). All three must be equal, and 0.6 is not.

Concept

When different percentages of different amounts give equal parts, each amount varies inversely with its percentage: the smaller the share taken, the larger the whole must be.

So A : B : C = 1⁄25 : 1⁄20 : 1⁄10. Multiply every term by 100 to clear the fractions: 4 : 5 : 10.

A screen before any arithmetic: the largest percentage belongs to the smallest amount. A takes 25%, so A is the smallest, and C, at 10%, is the largest.

That ordering alone rules out 10 : 5 : 4 and 5 : 4 : 10.

Key facts

If x% of A = y% of B, then A : B = y : x
25% = 1⁄4, 20% = 1⁄5, 10% = 1⁄10
Here A : B : C = 1⁄25 : 1⁄20 : 1⁄10 = 4 : 5 : 10

Study next

Equal fractions of three amounts, such as A⁄2 = B⁄3 = C⁄4Combining A : B and B : C into A : B : CDividing a sum in an inverse ratio

Common traps

Writing the percentages themselves, 25 : 20 : 10, as the ratio instead of their reciprocals
Getting 4, 5 and 10 right but assigning them to A, B and C in reverse

12 Sep 2025, 16:00, Quant Q.1 mixes the forms: 60% of A = 0.3 of B = 1⁄6 of C, keyed 5 : 10 : 18.

17 Sep 2024, 09:00, Quant Q.3 builds A : B : C from A : B = 6 : 8 and B : C = 7 : 10, keyed 21 : 28 : 40.

Related PYQs

No directly related past PYQ was found.

Topic: Percentage — all 66 SSC CGL questions on it, every solved shift.