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Caesar
Apple In A Bottle
The Crash
The Lift
The Job
The Son
Three Light Bulbs
The Square Field
The Bridge
Nine Coins
Two Fuses
The Two Robots

 

   

Puzzles & Brain Teasers

Nine Coins

You are given nine coins.
One of the coins is a fake and slightly lighter than the others but otherwise they all appear similar.
Using a simple balancing scale determine which is the fake coin.
You can use the scales TWICE only.

 

ANSWER

 

In other words...

Divide the coins into three sets of three.
Put one of the sets aside and weigh the remaining two sets.

If the scales balance then the fake coin is in the third set.
Take the third set, put one of the coins to one side and weigh the remaining two.
If again the scales balance the fake coin is the one which has been put aside. If the scales do not balance then the fake coin is the lighter of the pair.

If the scales do not balance then the fake coin is in the lighter set.
Take the lighter set and place one of the coins to one side. Weigh the remaining two. If the scales balance the fake is the one which has been put aside. If the scales do not balance then the fake coin is the lighter of the pair.

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