Answer:
To calculate how much items cost in US dollars when traveling to China or India, Karen will need to use the current foreign currency exchange rate. The exchange rate is the value of one country's currency in relation to another country's currency. For example, if the exchange rate between the US dollar and the Chinese yuan is 1 USD = 6.5 CNY, then one US dollar can be exchanged for 6.5 Chinese yuan.
Karen can use an online currency converter or mobile app to quickly and easily calculate the cost of items in US dollars. She can simply enter the amount of the foreign currency and select the currency she wants to convert to (in this case, US dollars). The currency converter will then give her the equivalent amount in US dollars based on the current exchange rate.
It's important to note that exchange rates can fluctuate over time, so Karen should check the current exchange rate before making any purchases to ensure she has an accurate understanding of the cost in US dollars.