UPSC Prelims 1999 · General Studies

Question 143: Basic Numeracy

If X + 2Y = 2X + Y, then X² / Y² is equal to

AnswerThe answer is (b).

X + 2Y = 2X + Y gives Y = X (move X and Y across: 2Y - Y = 2X - X). So X and Y are equal, and X squared over Y squared = 1 (taking Y as non-zero). Remember: simplify first, then substitute.

Why each option is right or wrong

(a) Wrong. The ratio would be 0 only if X were 0 while Y is not, but X = Y.
(b) Right. Y = X, so the ratio is 1.
(c) Wrong. 2 would need X squared to be twice Y squared.
(d) Wrong. 4 would need X = 2Y.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 1999, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.