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There are 15 gold coins. One of the gold coins is a fake. A fake gold coin is lighter than a real one. You have a “balance machine” without any scale. Can you identify the fake coin by using the “balance machine” at most three times? 

 Apr 6, 2021

Best Answer 

 #1
avatar+31287 
+2

Yes you can....is that what you wanted.....or an explanation as to how?

 

Starts this way   make 3 piles  7   7    1

   balance the 7's    if they balance, then the '1' is the fake

                                if they DON't balance, the lighter 7 has the fake

      take the lighter 7   make 3 piles   3  3  1

          balance the 3's   if they balance then the '1' is the fake

                                       if they don't balance then the lighter 3 has the fake

               take the lighter 3     make 3 piles  1  1   1

                    balance two of the 1's

                                             if they balance , the third '1' is the fake

                                                       if they don't balance , the lighter one is the fake .....with only THREE balances done !

 Apr 6, 2021
 #1
avatar+31287 
+2
Best Answer

Yes you can....is that what you wanted.....or an explanation as to how?

 

Starts this way   make 3 piles  7   7    1

   balance the 7's    if they balance, then the '1' is the fake

                                if they DON't balance, the lighter 7 has the fake

      take the lighter 7   make 3 piles   3  3  1

          balance the 3's   if they balance then the '1' is the fake

                                       if they don't balance then the lighter 3 has the fake

               take the lighter 3     make 3 piles  1  1   1

                    balance two of the 1's

                                             if they balance , the third '1' is the fake

                                                       if they don't balance , the lighter one is the fake .....with only THREE balances done !

ElectricPavlov Apr 6, 2021
 #2
avatar+118470 
0

Impressive, EP!!!!!

 

 

cool cool cool

CPhill  Apr 6, 2021

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