You have 5 jars of pills. Each pill weighs 10 grams, except for contaminated pills contained in one jar, where each pill weighs 9 grams. Given a scale, how could you tell which jar had the contaminated pills in just one measurement?
Take out 1 pill from jar 1, 2 pills from jar 2, 3 pills from jar 3, 4 pills from jar 4 and 5 pills from jar 5. Put all these 15 pills on scale. The correct wight is 150 (15*10). But one of the jars has contaminated pills. So the wight will definitely less than 150. If the wight is 149 then jar 1 has contaminated pills because the there is only one contaminated pill. If the wight is 148 then jar 2, if the wight is 147 then jar 3, if 146 then jar 4, if 145 then jar 5.
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