Electronic Weighing machine to find defective chocolate box puzzle

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You have ten chocolate boxes containing 10 chocolate each and an electronic weighing machine.

In those ten boxes,
you have chocolates. Each chocolate weigh 20 grams. But in one box the chocolates are defective and each weigh 19 grams exactly.

Now you can weigh in the electronic weighing machine but you can use that machine just once.
How will you find out which box has the defected chocolates.

chocolate box

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  • 1 Answer(s)
    Best answer

    Assuming that all boxes contain the same number of chocolates AND that the No. of chocolates per box is at least 10:

    Number the boxes as 1, 2, 3 etc.

    From each box,
    Take as many chocolates as its number. (i.e., take 1 chocolate from Box No. 1,  2 pieces from Box No. 2, 3 from No. 3 and so on. Total = 55) Now, weigh the selected chocolates together.
    If all chocolates were proper, the total weight would have been 1100 g. (55 * 20 g) Since each defective chocolate is 1 g less than the standard, the total weight would be less by as many grams as there are such defective chocolates in the selection. (e.g. if 5 defective chocolates were taken, the total weight would be 1105 g only.)
    Since the No. of chocolates taken is equal to the box number, the difference in weight (1100 – actual) would be the number of the box containing the defective ones.

    Viji_Pinarayi Expert Answered on 2nd January 2016.

    please correct the figure in 3rd last line , which should be 1095 g only

    on 23rd June 2016.
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