user3228: When A pays in USD but B receives EUR, how exactly does Ripple decide on the EUR/USD exchange rate?

user196: Since Ripple has an integrated exchange, I guess it simply places market orders in its order book, trying to get the best overall price.
You find the order book in Advanced/Trade, if you want to try manually.

3228: <p>When A pays in USD but B receives EUR, how exactly does Ripple decide on the EUR/USD exchange rate?</p>
 196: <p>Since Ripple has an integrated exchange, I guess it simply places market orders in its order book, trying to get the best overall price.</p>

<p>You find the order book in Advanced/Trade, if you want to try manually.</p>
