CREATE TABLE table_4856 ("Rank" FLOAT, "Nation" CLOB, "Gold" FLOAT, "Silver" FLOAT, "Bronze" FLOAT, "Total" FLOAT)

How many silver medals did the country that won 20 gold medals win in the 1955 Pan American Games?
SELECT SUM("Silver") FROM table_4856 WHERE "Gold" = '20'
SELECT SUM("Silver") FROM "table_4856" WHERE "Gold" = '20'