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A Pharmacist's Nightmare

You have 5 jars of pills. Each pill weighs 10 gram, except for contaminated pills contained in one jar, where each pill weighs 9 gm. Given a scale, how could you tell which jar had the contaminated pills in just one measurement?

see explanation

1. Mark the jars with numbers 1 – 5. 2. Take 1 pill from jar 1, take 2 pills from jar 2, and so on up to jar 5 3. Put all of them on the scale at once and take the measurement. 4. Now, subtract the measurement from 150 = ( 1*10 + 2*10 + 3*10 + 4*10 + 5*10) 5. The result will give you the jar number which has contaminated pill.


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Submitted by
over 7 years ago
Difficulty 7.0 ?