The Cigarette Puzzle - Brain Teaser

This is a brain teaser that is very short and extremely hard for adults.

This is the puzzle

1. There are 10 packets of cigarette. All packets hold 10 cigarettes.
2. 9 packets have cigarettes of 10 grams. 1 packet has cigarettes of 11 grams.
3. How would you identify the packet having 11 grams cigarettes? You are given a digital weighing machine, and you have just one chance to weigh.

Solution is given below.

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Cigarette Puzzle Answer

1. Mark all packets - 1 to 10. Pick 1 cigarette from packet 1, 2 cigarettes from packet 2, 3 cigarettes from packet 3 and so on till 10 cigarettes from packet 10.
2. Weigh the cigarettes. We have total 55 cigarettes to weigh. If all cigarettes were 10 grams, the weight would be 550 grams.
3. The excess weight (over 550 grams) would indicate the serial number of the packet having 11 grams cigarettes.
   Example: Suppose the weight is 554 grams, there are 4 cigarettes weighing 11 grams. Hence, it’s packet no. 4. It’s from packet #4 that I have picked 4 cigarettes.