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Solution By psyang on Tuesday, August 29, 2006 (UMST)

Take 1 pill from jar 1, 2 pills from jar 2, 3 pills from jar 3, and 4 pills from jar 4, then weigh all 10 pills together. The total weight will be 10*weight + k, where k = # of contaminated pills that were measured. Thus, if k=1, the contaminated jar is jar 1, or if k=2, the contaminated jar is jar 2, etc.   Another interesting side point. You only need to take pills out of 3 jars (1 from jar1, 2 from jar2, and 3 from jar3). If the weight = 6*weight, then the contaminated jar is jar 1, otherwise proceed as usual. This is how you can determine the contaminated jar in one weighing with the minimal number of pills involved (assuming you can't break up a pill). Reply to this Comment