Because the US dollar (USD) is the primary currency for mutual settlements worldwide, exchange rates are often expressed in US dollars and are also used as the basis for cross-ratings. For example, EURJPY is the cross rate of EURUSD and USDJPY. The US dollar does not take part in the currency pair, but it exists and its market changes affect the EUR/JPY rate. If you know the current USDEUR and USDGBP exchange rates, you can multiply them and get a quote for the EURGBP pair. As with currency pairs that include the US dollar, the base currency is always equal to 1 and the amount changes relative to the second quote currency.