UPSC Prelims 2026 · CSAT Paper 2 · Set DMathematicsQ 45 / 80

UPSC Prelims 2026 CSAT Paper 2 — Question 45

Question

An alloy P contains 20% copper and 80% zinc by weight. Another alloy Q contains 60% copper and 40% zinc by weight. A third alloy R is to be prepared from P and Q so that it contains equal amount of copper and zinc. In what ratio, amounts of P and Q be mixed in order to get R?

(a)1 : 3
(b)3 : 1
(c)2 : 3
(d)3 : 2

UnlockIAS answer: (a)1 : 3

Solution

By alligation on copper (20% and 60% to a target of 50%): P : Q = (60 − 50) : (50 − 20) = 10 : 30 = 1 : 3.

UnlockIAS expert key, prepared 24 May 2026 and cross-verified by re-deriving the answer — this is our key, not the official UPSC provisional key (awaited).

Section

Mathematics

Topic Reference

Numeracy — Alligation (alloys)

Official UPSC key still awaited

UPSC has announced (PIB Release 2262441, 18 May 2026) that the provisional answer key for CSE Prelims 2026 will be released “soon after Exam”. Until then, use the CSAT score calculator for your qualifying-status estimate, and join the per-question discussion below.

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Official Notification

PIB Release 2262441

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