Defective stack of coins puzzle

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There are 10 stacks of 10 coins each.
Each coin weights 10 gms. However, one stack of coins is defective and each coin in that stack weights only 9 gms.

What is the minimum number of weights you need to take to find which stack is defective? How?

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    SOLUTION-   1 Measurement Only

    EXPLANATION-
    We will take,
    1 coin from the first stack,
    2 coins from the second,
    3 from the third
    and
    so on.

    In total we will have 55 coins.
    If all of them were non-defective, they would weigh 550 gms.
    If stack 1 is defective, the measure would read 549 gms.
    If stack 2 is defective, you will read 548 gms.
    and so on.

    So by taking one measurement you can identify, which is the defective stack.

    MrPuzzleFry Genius Answered on 11th September 2015.
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