Question
What is the minimum number of times one needs to measure to get 298 litres of water from a tank, if the measuring cylinders have capacities 1 litre, 6 litres, 25 litres and 100 litres?
- (a)4
- (b)5
- (c)9
- (d)13
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298 = 3 × 100 − 2 × 1, i.e. three fillings of 100 L and two removals of 1 L — five operations. No combination of four measurements reaches 298.
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).
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