# 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?

SherlockHolmes Expert Asked on 11th September 2015 in

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 Pundit Answered on 11th September 2015.

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