IQ Brain Teaser #190
Sacks marked A, B, C, D, E and F each contain 100 coins. 5 of the sacks contain coins that are exactly alike in all respects, including weight: 1 ounce per coin. One of the sacks contains coins that look exactly like the coins in the other sacks, but each coin in this sack weighs 1.1 ounces. Using an electronic scale exactly one time, how can you determine, with certainty, which sack contains the coins that weigh 1.1 ounces?

By placing all of the sacks with all of their coins in them on the scale at the same time
By removing all of the coins from the sacks, and weighing all of the sacks at the same time
By removing all of the coins from the sacks, and weighing all of the coins at the same time
By removing 1 coin from each sack, and weighing only those 6 coins
By removing 2 coins from each sack, and weighing only those 12 coins
By removing 7 coins from each sack, and weighing only those 42 coins
By removing 11 coins from each sack, and weighing only those 66 coins
By removing 13 coins from each sack, and weighing only those 78 coins
By removing 17 coins from each sack, and weighing only those 102 coins
None of the above are correct

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