UPSC Prelims 2026 · CSAT Paper 2 · Set DMathematicsQ 3 / 80

UPSC Prelims 2026 CSAT Paper 2 — Question 3

Question

There are four types of weights, namely 1 kg, 2 kg, 5 kg and 10 kg. What is the maximum number of different ways one can measure 20 kg, if at least eight but not more than eleven weights of 1 kg are to be used while measuring?

(a)7
(b)8
(c)9
(d)10

UnlockIAS answer: (b)8

Solution

Solving a + 2b + 5c + 10d = 20 with 8 ≤ a ≤ 11 (a, b, c, d ≥ 0) yields exactly 8 valid combinations.

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 — Counting with constraints

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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