Problem #48 EASY
The Night Watchman's Dilemma
Scenario Logic Deduction Physics
Problem Statement
Rajan has worked the night shift at a textile warehouse in Surat for eleven years. He knows every corner of the building, every creak of the floorboards, every shadow.
One Tuesday evening, just as he settles into his chair with a thermos of chai, the power cuts out. The entire building goes dark. Rajan reaches into his drawer and pulls out a torch — but the batteries are dead.
He needs to go downstairs to reset the circuit breaker, which means passing through the storage room. Inside that room are two large barrels. One barrel is filled with engine oil. The other is filled with drinking water. Both barrels look identical in the dark — same size, same shape, same material.
Rajan knows that earlier in the week, a worker spilled some drinking water near the water barrel and some engine oil near the oil barrel. The floor around each barrel still carries the faint smell of whatever is inside.
He kneels down and sniffs near one barrel. It smells faintly of water.
Without any light, without opening the barrels, and without tasting or pouring anything — how can Rajan confirm with complete certainty which barrel contains water and which contains oil?
Answer & Quick Explanation
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The barrel whose surrounding floor smells of water is the water barrel. The other is the oil barrel. The earlier spills left behind scent-based identification markers. Rajan simply uses his sense of smell on the floor — no light needed.
Detailed Editorial Solution
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Puzzles like this one test whether solvers look for complexity when the answer is sitting right in the problem statement. All the information needed is already given — the floor around each barrel carries the smell of its contents from the earlier spill.
Step 1: The problem states that a worker spilled drinking water near the water barrel earlier that week.
Step 2: It also states that engine oil was spilled near the oil barrel. Both spills remain on the floor.
Step 3: Rajan kneels and sniffs near one barrel — it smells of water. This means the water spill is near this barrel, identifying it as the water barrel.
Step 4: The other barrel, by elimination, is the oil barrel. No light, no tasting, no opening required.
Step 5: The sensory information — smell — was already present in the environment. Rajan simply needed to use it.
Step 6: This is confirmed without ambiguity: a water-smelling floor means water was stored there, and an oil-smelling floor means oil was stored there.
Key Insight:
The best puzzles hide the solution inside the problem description itself. The spill detail is not flavour text — it is the answer. Training yourself to treat every detail in a problem as potentially load-bearing is the core skill this puzzle teaches.