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Mateen Ulhaq
Mateen Ulhaq
  • 99
  • 4

Odd $N$

Mark all the coins with $c_1, c_2,\ldots,c_N$.

Pick one coin, $c_k$. Weigh all other coins on the balance, putting half on either side.

  • If the balance is equal, $c_k$ is fake.
  • If the balance is unbalanced, repeat the above process for a different value of $k$ each time.$c_k$ is genuine and we have reduced our problem to even $N\geq 2$

Odd $N$

Mark all the coins with $c_1, c_2,\ldots,c_N$.

Pick one coin, $c_k$. Weigh all other coins on the balance, putting half on either side.

  • If the balance is equal, $c_k$ is fake.
  • If the balance is unbalanced, repeat the above process for a different value of $k$ each time.

Odd $N$

Mark all the coins with $c_1, c_2,\ldots,c_N$.

Pick one coin, $c_k$. Weigh all other coins on the balance, putting half on either side.

  • If the balance is equal, $c_k$ is fake.
  • If the balance is unbalanced, $c_k$ is genuine and we have reduced our problem to even $N\geq 2$
Made sure folks don't miss an important detail.
Source Link
Mateen Ulhaq
Mateen Ulhaq
  • 99
  • 4

Odd $N$

Mark all the coins with $c_1, c_2,\ldots,c_N$.

Pick one coin, $c_k$. Weigh all other coinsall other coins on the balance, putting half on either side.

  • If the balance is equal, $c_k$ is fake.
  • If the balance is unbalanced, repeat the above process for a different value of $k$ each time.

Odd $N$

Mark all the coins with $c_1, c_2,\ldots,c_N$.

Pick one coin, $c_k$. Weigh all other coins on the balance, putting half on either side.

  • If the balance is equal, $c_k$ is fake.
  • If the balance is unbalanced, repeat the above process for a different value of $k$ each time.

Odd $N$

Mark all the coins with $c_1, c_2,\ldots,c_N$.

Pick one coin, $c_k$. Weigh all other coins on the balance, putting half on either side.

  • If the balance is equal, $c_k$ is fake.
  • If the balance is unbalanced, repeat the above process for a different value of $k$ each time.
Source Link
Mateen Ulhaq
Mateen Ulhaq
  • 99
  • 4

Odd $N$

Mark all the coins with $c_1, c_2,\ldots,c_N$.

Pick one coin, $c_k$. Weigh all other coins on the balance, putting half on either side.

  • If the balance is equal, $c_k$ is fake.
  • If the balance is unbalanced, repeat the above process for a different value of $k$ each time.