What ’ s “ pi ” ?   That ’ s the ratio of the circumference of a circle to its diameter , I think .   I see . What is that ratio exactly ?   It ’ s approximately 3.14 , but the number continues forever . What ’ s the diameter of your circle ?   It ’ s 10 centimeters , so the circumference should be 31.4 centimeters .   Ok . My next problem is to convert 10000 british pounds into us dollars . What ’ s the exchange rate at the moment ?   According to the newspaper , the exchange rate is 1.85 dollars to the pound .   That means that 10.000 pounds will buy me 18.500 dollars . 