when did the dollar became the world currency
Reserve currency By the end of the 20th century, the United States dollar was considered the world's most dominant reserve currency.[1] The world's need for dollars has allowed the United States government as well as Americans to borrow at lower costs, granting them an advantage in excess of $100 billion per year.[2]
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United States one-dollar bill The United States one-dollar bill    ($1) is a denomination of United States currency. An image of the first U.S. President (1789â€“97), George Washington, based on a painting by Gilbert Stuart, is currently featured on the obverse (front), and the Great Seal of the United States is featured on the reverse (back). The one-dollar bill has the oldest overall design of all U.S. currency currently being produced (The current two-dollar bill obverse design dates from 1928, while the reverse appeared in 1976). The obverse design of the dollar bill seen today debuted in 1963 (the reverse in 1935) when it was first issued as a Federal Reserve Note (previously, one dollar bills were Silver Certificates).
Decimalisation India changed from the rupee, anna, pie system to decimal currency on 1 April 1957.