Puzzle | Find the Jar with Contaminated Pills

You have 5 jars of pills. Each pill in a jar normally weighs 10 grams, but one of the jars is contaminated, and every pill in that jar weighs 9 grams instead of 10.

You are allowed to use a digital weighing scale only once.

How can you determine which jar contains the contaminated pills using just one measurement?

Check if you were right - full answer with solution below.

Solution:

To find the contaminated Jar, follow this step-wise approach :

Step 1: 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.

Step 2: Put all these 15 pills on the scale. The correct weight is 150 (15*10). But one of the jars has contaminated pills. So the weight will definitely be less than 150.

Step 3: If the weight is 149 then jar 1 has contaminated pills because there is only one contaminated pill. If the weight is 148 then jar 2, if the weight is 147 then jar 3, if 146 then jar 4, if 145 then jar 5.