1. The problem is to convert 40 US dollars into Japanese yen. 2. The formula for currency conversion is: $$\text{Amount in yen} = \text{Amount in dollars} \times \text{Exchange rate}$$ 3. The exchange rate varies daily; for example, if the exchange rate is 1 dollar = 135 yen, then: 4. Substitute the values: $$40 \times 135 = 5400$$ 5. Therefore, 40 dollars is equivalent to 5400 yen at this exchange rate. 6. Remember, the exact amount depends on the current exchange rate, so check the latest rate for precise conversion.