Given:
1 dollar=\(\displaystyle\frac{{1}}{{20}}\) ounce of gold

1 Swiss franc=\(\displaystyle\frac{{1}}{{40}}\) ounce of gold

Since \(\displaystyle\frac{{1}}{{20}}=\frac{{2}}{{40}}={2}\cdot\frac{{1}}{{40}}:\)

1 dollar=\(\displaystyle\frac{{1}}{{20}}\) ounce of gold

\(\displaystyle={2}\cdot\frac{{1}}{{40}}\) ounce of gold \(\displaystyle={2}\cdot{1}\) Swiss franc =2 Swiss franc

Thus the exchange rate between dollars and Swiss francs is 2 Swiss francs for every dollar.

1 Swiss franc=\(\displaystyle\frac{{1}}{{40}}\) ounce of gold

Since \(\displaystyle\frac{{1}}{{20}}=\frac{{2}}{{40}}={2}\cdot\frac{{1}}{{40}}:\)

1 dollar=\(\displaystyle\frac{{1}}{{20}}\) ounce of gold

\(\displaystyle={2}\cdot\frac{{1}}{{40}}\) ounce of gold \(\displaystyle={2}\cdot{1}\) Swiss franc =2 Swiss franc

Thus the exchange rate between dollars and Swiss francs is 2 Swiss francs for every dollar.